How to change where asset_path looks?
You can set the url path via config.assets.prefix and the place where assets are looked for is configured with config.assets.paths.
From the guide on configuring assets:
config.assets.pathscontains the paths which are used to look for assets. Appending paths to this configuration option will cause those paths to be used in the search for assets.
config.assets.prefixdefines the prefix where assets are served from. Defaults to /assets.