Gas pressure/Used parts '83 320i

My car was just diagnosed with a bad fuel pump, unfortuanatly a new one is $500, and it is not worth it. Does anyone know where I can get a used fuel pump that is compatible with the car? My mechanic replaced the fuel filter but is still not getting pressure, does anyone know any other reason this might be? If you know of a junkyard, or the like, I live around Chicago, Illinois.