Chainsaws

The chainsaw itself doesn't have a model# on it, just the serial# and other misc. numbers. I'm trying to find a gas cap for it since it's leaking either from the gasket and/or pin-hole that allows vapors to escape (I'm guessing that is why there is a fine pin size hole in the center of the cap). The instruction manual for this saw does not have a parts list nor illustration. Do you have any suggestions on how I could obtain the cap, model #, and parts list/illustration?