not a complete answer, but have you considered creating your own scrollbar lookalike:

import tkinter as tkclass MyScrollbar(tk.Canvas):    def __init__(self, master, *args, **kwargs):        if 'width' not in kwargs:            kwargs['width'] = 10        if 'bd' not in kwargs:            kwargs['bd'] = 0        if 'highlightthickness' not in kwargs:            kwargs['highlightthickness'] = 0        self.command = kwargs.pop('command')                tk.Canvas.__init__(self, master, *args, **kwargs)                self.elements = {   'button-1':None,                            'button-2':None,                            'trough':None,                            'thumb':None}                self._oldwidth = 0        self._oldheight = 0                self._sb_start = 0        self._sb_end = 1                self.bind('<Configure>', self._resize)        self.tag_bind('button-1', '<Button-1>', self._button_1)        self.tag_bind('button-2', '<Button-1>', self._button_2)        self.tag_bind('trough', '<Button-1>', self._trough)                self._track = False        self.tag_bind('thumb', '<ButtonPress-1>', self._thumb_press)        self.tag_bind('thumb', '<ButtonRelease-1>', self._thumb_release)        self.tag_bind('thumb', '<Leave>', self._thumb_release)                self.tag_bind('thumb', '<Motion>', self._thumb_track)                def _sort_kwargs(self, kwargs):        for key in kwargs:            if key in ['buttontype', 'buttoncolor', 'troughcolor', 'thumbcolor', 'thumbtype']:                self._scroll_kwargs[key] = kwargs.pop(key) # add to custom dict and remove from canvas dict        return kwargs                    def _resize(self, event):        width = self.winfo_width()        height = self.winfo_height()#       print("canvas: (%s, %s)" % (width, height))        if self.elements['button-1']: # exists            if self._oldwidth != width:                self.delete(self.elements['button-1'])                self.elements['button-1'] = None            else:                pass        if not self.elements['button-1']: # create            self.elements['button-1'] = self.create_oval((0,0,width, width), fill='#006cd9', outline='#006cd9', tag='button-1')                                if self.elements['button-2']: # exists            coords = self.coords(self.elements['button-2'])            if self._oldwidth != width:                self.delete(self.elements['button-2'])                self.elements['button-2'] = None            elif self._oldheight != height:                self.move(self.elements['button-2'], 0, height-coords[3])            else:                pass        if not self.elements['button-2']: # create            self.elements['button-2'] = self.create_oval((0,height-width,width, height), fill='#006cd9', outline='#006cd9', tag='button-2')                if self.elements['trough']: # exists            coords = self.coords(self.elements['trough'])            if (self._oldwidth != width) or (self._oldheight != height):                self.delete(self.elements['trough'])                self.elements['trough'] = None            else:                pass        if not self.elements['trough']: # create            self.elements['trough'] = self.create_rectangle((0,int(width/2),width, height-int(width/2)), fill='#00468c', outline='#00468c', tag='trough')        self.set(self._sb_start, self._sb_end) # hacky way to redraw thumb        self.tag_raise('thumb') # ensure thumb always on top of trough                    self._oldwidth = width        self._oldheight = height            def _button_1(self, event):        self.command('scroll', -1, 'pages')        return 'break'        def _button_2(self, event):        self.command('scroll', 1, 'pages')        return 'break'            def _trough(self, event):        width = self.winfo_width()        height = self.winfo_height()                size = (self._sb_end - self._sb_start) / 1                thumbrange = height - width        thumbsize = int(thumbrange * size)        thumboffset = int(thumbrange * self._sb_start) + int(width/2)                thumbpos = int(thumbrange * size / 2) + thumboffset        if event.y < thumbpos:            self.command('scroll', -1, 'pages')        elif event.y > thumbpos:            self.command('scroll', 1, 'pages')        return 'break'        def _thumb_press(self, event):        print("thumb press: (%s, %s)" % (event.x, event.y))        self._track = True            def _thumb_release(self, event):        print("thumb release: (%s, %s)" % (event.x, event.y))        self._track = False            def _thumb_track(self, event):        if self._track:#           print("*"*30)            print("thumb: (%s, %s)" % (event.x, event.y))            width = self.winfo_width()            height = self.winfo_height()        #           print("window size: (%s, %s)" % (width, height))                    size = (self._sb_end - self._sb_start) / 1#           print('size: %s' % size)            thumbrange = height - width#           print('thumbrange: %s' % thumbrange)            thumbsize = int(thumbrange * size)#           print('thumbsize: %s' % thumbsize)            clickrange = thumbrange - thumbsize#           print('clickrange: %s' % clickrange)            thumboffset = int(thumbrange * self._sb_start) + int(width/2)#           print('thumboffset: %s' % thumboffset)                    thumbpos = int(thumbrange * size / 2) + thumboffset        #           print("mouse point: %s" % event.y)#           print("thumbpos: %s" % thumbpos)                    point = (event.y - (width/2) - (thumbsize/2)) / clickrange#           point = (event.y - (width / 2)) / (thumbrange - thumbsize)#           print(event.y - (width/2))#           print(point)            if point < 0:                point = 0            elif point > 1:                point = 1#           print(point)            self.command('moveto', point)            return 'break'            def set(self, *args):        oldsize = (self._sb_end - self._sb_start) / 1                self._sb_start = float(args[0])        self._sb_end = float(args[1])                size = (self._sb_end - self._sb_start) / 1                width = self.winfo_width()        height = self.winfo_height()                if oldsize != size:            self.delete(self.elements['thumb'])            self.elements['thumb'] = None                thumbrange = height - width        thumbsize = int(thumbrange * size)        thumboffset = int(thumbrange * self._sb_start) + int(width/2)                if not self.elements['thumb']: # create            self.elements['thumb'] = self.create_rectangle((0, thumboffset,width, thumbsize+thumboffset), fill='#4ca6ff', outline='#4ca6ff', tag='thumb')        else: # move            coords = self.coords(self.elements['thumb'])            if (thumboffset != coords[1]):                self.move(self.elements['thumb'], 0, thumboffset-coords[1])        return 'break'        if __name__ == '__main__':    root = tk.Tk()    lb = tk.Listbox(root)    lb.pack(side='left', fill='both', expand=True)    for num in range(0,100):        lb.insert('end', str(num))            sb = MyScrollbar(root, width=50, command=lb.yview)    sb.pack(side='right', fill='both', expand=True)        lb.configure(yscrollcommand=sb.set)    root.mainloop()

I've left my comments in, and for the life of me i can't seem to get click and dragging the thumb to work correctly, but its a simple scrollbar with the following features:

• up and down buttons that can be coloured
• thumb and trough that can be individually coloured
• tracks movement in scrollable widget
• thumb resizes with size of scroll area

Edit

I've revised the thumb code to fix the click and drag scrolling:

import tkinter as tkclass MyScrollbar(tk.Canvas):    def __init__(self, master, *args, **kwargs):        self._scroll_kwargs = { 'command':None,                                'orient':'vertical',                                'buttontype':'round',                                'buttoncolor':'#006cd9',                                'troughcolor':'#00468c',                                'thumbtype':'rectangle',                                'thumbcolor':'#4ca6ff',                                }                kwargs = self._sort_kwargs(kwargs)        if self._scroll_kwargs['orient'] == 'vertical':            if 'width' not in kwargs:                kwargs['width'] = 10        elif self._scroll_kwargs['orient'] == 'horizontal':            if 'height' not in kwargs:                kwargs['height'] = 10        else:            raise ValueError        if 'bd' not in kwargs:            kwargs['bd'] = 0        if 'highlightthickness' not in kwargs:            kwargs['highlightthickness'] = 0                tk.Canvas.__init__(self, master, *args, **kwargs)                self.elements = {   'button-1':None,                            'button-2':None,                            'trough':None,                            'thumb':None}                self._oldwidth = 0        self._oldheight = 0                self._sb_start = 0        self._sb_end = 1                self.bind('<Configure>', self._resize)        self.tag_bind('button-1', '<Button-1>', self._button_1)        self.tag_bind('button-2', '<Button-1>', self._button_2)        self.tag_bind('trough', '<Button-1>', self._trough)                self._track = False        self.tag_bind('thumb', '<ButtonPress-1>', self._thumb_press)        self.bind('<ButtonRelease-1>', self._thumb_release)#       self.bind('<Leave>', self._thumb_release)                self.bind('<Motion>', self._thumb_track)                def _sort_kwargs(self, kwargs):        to_remove = []        for key in kwargs:            if key in [ 'buttontype', 'buttoncolor', 'buttonoutline',                        'troughcolor', 'troughoutline',                        'thumbcolor', 'thumbtype', 'thumboutline',                        'command', 'orient']:                self._scroll_kwargs[key] = kwargs[key] # add to custom dict                to_remove.append(key)                        for key in to_remove:            del kwargs[key]        return kwargs            def _get_colour(self, element):        if element in self._scroll_kwargs: # if element exists in settings            return self._scroll_kwargs[element]        if element.endswith('outline'): # if element is outline and wasn't in settings            return self._scroll_kwargs[element.replace('outline', 'color')] # fetch default for main element            def _width(self):        return self.winfo_width() - 2 # return width minus 2 pixes to ensure fit in canvas            def _height(self):        return self.winfo_height() - 2 # return height minus 2 pixes to ensure fit in canvas                    def _resize(self, event):        width = self._width()        height = self._height()        if self.elements['button-1']: # exists            # delete element if vertical scrollbar and width changed            # or if horizontal and height changed, signals button needs to change            if (((self._oldwidth != width) and (self._scroll_kwargs['orient'] == 'vertical')) or                ((self._oldheight != height) and (self._scroll_kwargs['orient'] == 'horizontal'))):                self.delete(self.elements['button-1'])                self.elements['button-1'] = None        if not self.elements['button-1']: # create            size = width if (self._scroll_kwargs['orient'] == 'vertical') else height            rect = (0,0,size, size)            fill = self._get_colour('buttoncolor')            outline = self._get_colour('buttonoutline')            if (self._scroll_kwargs['buttontype'] == 'round'):                self.elements['button-1'] = self.create_oval(rect, fill=fill, outline=outline, tag='button-1')            elif (self._scroll_kwargs['buttontype'] == 'square'):                self.elements['button-1'] = self.create_rectangle(rect, fill=fill, outline=outline, tag='button-1')                    if self.elements['button-2']: # exists            coords = self.coords(self.elements['button-2'])            # delete element if vertical scrollbar and width changed            # or if horizontal and height changed, signals button needs to change            if (((self._oldwidth != width) and (self._scroll_kwargs['orient'] == 'vertical')) or                ((self._oldheight != height) and (self._scroll_kwargs['orient'] == 'horizontal'))):                self.delete(self.elements['button-2'])                self.elements['button-2'] = None            # if vertical scrollbar and height changed button needs to move            elif ((self._oldheight != height) and (self._scroll_kwargs['orient'] == 'vertical')):                self.move(self.elements['button-2'], 0, height-coords[3])            # if horizontal scrollbar and width changed button needs to move            elif ((self._oldwidth != width) and (self._scroll_kwargs['orient'] == 'horizontal')):                self.move(self.elements['button-2'], width-coords[2], 0)        if not self.elements['button-2']: # create            if (self._scroll_kwargs['orient'] == 'vertical'):                rect = (0,height-width,width, height)            elif (self._scroll_kwargs['orient'] == 'horizontal'):                rect = (width-height,0,width, height)            fill = self._get_colour('buttoncolor')            outline = self._get_colour('buttonoutline')            if (self._scroll_kwargs['buttontype'] == 'round'):                self.elements['button-2'] = self.create_oval(rect, fill=fill, outline=outline, tag='button-2')            elif (self._scroll_kwargs['buttontype'] == 'square'):                self.elements['button-2'] = self.create_rectangle(rect, fill=fill, outline=outline, tag='button-2')                if self.elements['trough']: # exists            coords = self.coords(self.elements['trough'])            # delete element whenever width or height changes            if (self._oldwidth != width) or (self._oldheight != height):                self.delete(self.elements['trough'])                self.elements['trough'] = None        if not self.elements['trough']: # create            if (self._scroll_kwargs['orient'] == 'vertical'):                rect = (0, int(width/2), width, height-int(width/2))            elif (self._scroll_kwargs['orient'] == 'horizontal'):                rect = (int(height/2), 0, width-int(height/2), height)            fill = self._get_colour('troughcolor')            outline = self._get_colour('troughoutline')            self.elements['trough'] = self.create_rectangle(rect, fill=fill, outline=outline, tag='trough')        self.set(self._sb_start, self._sb_end) # hacky way to redraw thumb without moving it        self.tag_raise('thumb') # ensure thumb always on top of trough                    self._oldwidth = width        self._oldheight = height            def _button_1(self, event):        command = self._scroll_kwargs['command']        if command:            command('scroll', -1, 'pages')        return 'break'        def _button_2(self, event):        command = self._scroll_kwargs['command']        if command:            command('scroll', 1, 'pages')        return 'break'            def _trough(self, event):#       print('trough: (%s, %s)' % (event.x, event.y))        width = self._width()        height = self._height()                coords = self.coords(self.elements['trough'])                if (self._scroll_kwargs['orient'] == 'vertical'):            trough_size = coords[3] - coords[1]        elif (self._scroll_kwargs['orient'] == 'horizontal'):            trough_size = coords[2] - coords[0]#       print('trough size: %s' % trough_size)                size = (self._sb_end - self._sb_start) / 1        if (self._scroll_kwargs['orient'] == 'vertical'):            thumbrange = height - width        elif (self._scroll_kwargs['orient'] == 'horizontal'):            thumbrange = width - height        thumbsize = int(thumbrange * size)                if (self._scroll_kwargs['orient'] == 'vertical'):            thumboffset = int(thumbrange * self._sb_start) + int(width/2)        elif (self._scroll_kwargs['orient'] == 'horizontal'):            thumboffset = int(thumbrange * self._sb_start) + int(height/2)        thumbpos = int(thumbrange * size / 2) + thumboffset                command = self._scroll_kwargs['command']        if command:            if (((self._scroll_kwargs['orient'] == 'vertical') and (event.y < thumbpos)) or                ((self._scroll_kwargs['orient'] == 'horizontal') and (event.x < thumbpos))):                command('scroll', -1, 'pages')            elif (((self._scroll_kwargs['orient'] == 'vertical') and (event.y > thumbpos)) or                ((self._scroll_kwargs['orient'] == 'horizontal') and (event.x > thumbpos))):                command('scroll', 1, 'pages')        return 'break'        def _thumb_press(self, event):        self._track = True            def _thumb_release(self, event):        self._track = False                def _thumb_track(self, event):#       print('track')        if self._track:            width = self._width()            height = self._height()#           print("window size: (%s, %s)" % (width, height))                        size = (self._sb_end - self._sb_start) / 1                        coords = self.coords(self.elements['trough'])#           print('trough coords: %s' % coords)                        if (self._scroll_kwargs['orient'] == 'vertical'):                trough_size = coords[3] - coords[1]                thumbrange = height - width            elif (self._scroll_kwargs['orient'] == 'horizontal'):                trough_size = coords[2] - coords[0]                thumbrange = width - height#           print('trough size: %s' % trough_size)                            thumbsize = int(thumbrange * size)                        if (self._scroll_kwargs['orient'] == 'vertical'):                pos = max(min(trough_size, event.y - coords[1] - (thumbsize/2)), 0)            elif (self._scroll_kwargs['orient'] == 'horizontal'):                pos = max(min(trough_size, event.x - coords[0] - (thumbsize/2)), 0)            #           print('pos: %s' % pos)                        point = pos / trough_size#           print('point: %s' % point)                        command = self._scroll_kwargs['command']            if command:                command('moveto', point)            return 'break'            def set(self, *args):#       print('set: %s' % str(args))        oldsize = (self._sb_end - self._sb_start) / 1                self._sb_start = float(args[0])        self._sb_end = float(args[1])                size = (self._sb_end - self._sb_start) / 1                width = self._width()        height = self._height()                if oldsize != size:            self.delete(self.elements['thumb'])            self.elements['thumb'] = None                if (self._scroll_kwargs['orient'] == 'vertical'):            thumbrange = height - width            thumboffset = int(thumbrange * self._sb_start) + int(width/2)        elif (self._scroll_kwargs['orient'] == 'horizontal'):            thumbrange = width - height            thumboffset = int(thumbrange * self._sb_start) + int(height/2)        thumbsize = int(thumbrange * size)                if not self.elements['thumb']: # create            if (self._scroll_kwargs['orient'] == 'vertical'):                rect = (0, thumboffset,width, thumbsize+thumboffset)            elif (self._scroll_kwargs['orient'] == 'horizontal'):                rect = (thumboffset, 0, thumbsize+thumboffset, height)            fill = self._get_colour('thumbcolor')            outline = self._get_colour('thumboutline')            if (self._scroll_kwargs['thumbtype'] == 'round'):                self.elements['thumb'] = self.create_oval(rect, fill=fill, outline=outline, tag='thumb')            elif (self._scroll_kwargs['thumbtype'] == 'rectangle'):                self.elements['thumb'] = self.create_rectangle(rect, fill=fill, outline=outline, tag='thumb')        else: # move            coords = self.coords(self.elements['thumb'])            if (self._scroll_kwargs['orient'] == 'vertical'):                if (thumboffset != coords[1]):                    self.move(self.elements['thumb'], 0, thumboffset-coords[1])            elif (self._scroll_kwargs['orient'] == 'horizontal'):                if (thumboffset != coords[1]):                    self.move(self.elements['thumb'], thumboffset-coords[0], 0)        return 'break'        if __name__ == '__main__':    root = tk.Tk()    root.grid_rowconfigure(1, weight=1)    root.grid_columnconfigure(1, weight=1)        root.grid_rowconfigure(3, weight=1)    root.grid_columnconfigure(3, weight=1)        lb = tk.Listbox(root)    lb.grid(column=1, row=1, sticky="nesw")    for num in range(0,100):        lb.insert('end', str(num)*100)            sby1 = MyScrollbar(root, width=50, command=lb.yview)    sby1.grid(column=2, row=1, sticky="nesw")        sby2 = MyScrollbar(root, width=50, command=lb.yview, buttontype='square', thumbtype='round')    sby2.grid(column=4, row=1, sticky="nesw")        sbx1 = MyScrollbar(root, height=50, command=lb.xview, orient='horizontal', buttoncolor='red', thumbcolor='orange', troughcolor='green')    sbx1.grid(column=1, row=2, sticky="nesw")        sbx2 = MyScrollbar(root, height=50, command=lb.xview, orient='horizontal', thumbtype='round')    sbx2.grid(column=1, row=4, sticky="nesw")        def x_set(*args):        sbx1.set(*args)        sbx2.set(*args)            def y_set(*args):        sby1.set(*args)        sby2.set(*args)        lb.configure(yscrollcommand=y_set, xscrollcommand=x_set)    root.mainloop()

so I've fixed the calculation to work out where the new scroll to position will be, and changed from binding on the thumb tag for the track and release events to binding on the whole canvas, so if the user scrolls quickly the binding will still release when the mouse is let go.
I've commented out the binding for when the cursor leaves the canvas so the behavior more closely mimics the existing scroll bar, but can be re enabled if you want it to stop scrolling if the mouse leaves the widget.
As for making two classes, the amended code above lets you use the orient keyword so you can just drop this class (with styling changes) in place of the default scrollbar, as shown in the example at the bottom.