In response to
aberfroman's
comment from Dec 18, 2009:
The technique is to take the "engine" model number off of the engine and use THAT number to look up the engine-related parts - like a gas cap.
Remarkably, Parts Direct does not list or have a link from the engine to the engine parts list on its site.
You'll need to look for the stamped in numbers, right off the engine, itself.