Ken7234- Welcome to Trains.com!
Darren (BLHS & CRRM Lifetime Member)
Delaware and Hudson Virtual Museum (DHVM), Railroad Adventures (RRAdventures)
You will of course hear about the ebay suggestion--lol.
Anyway, what I would do is to contact NWSL and they can get you what you need. It should be better than OEM. Some Athearn parts are interchangeable, but that depends on the generation of your loco and the generation of the Athearn loco. If yours is a blue or brown colored box then the Athearn locos of the 90s(more or less) may have some interchangeable parts. But you can just call NWSL and they'll know what you need.
Model Railroader magazine