Is there a way to pass params to a Flask-Restless GET_SINGLE preprocessor?
As @1.618 pointed out, my particular use case is better suited for a GET_MANY request, even if I'm only expected a single item in response. I'm still unsure of the answer to my initial question, but my intuition is that that no, there is not a way to pass params to a GET_SINGLE request, as in Flask-restless they are only intended for scenarios where an item is queried by id.
The solution to my particular problem was to use a GET_MANY request instead, which I had initially tried but couldn't get to work due to my incorrectly manipulating the search_params argument and my confusion surrounding how variables are passed in Python.