Kevin-
Here is the website. They operate out of Arizona. I would try Preferred parts also. The parts for your aircraft are available for the most part. Finding the best price is the hard part for many items.
Premier -
http://www.iwantcessnaparts.com/
-
http://www.cessnaparts.com/
Preferred/New and Salvage -
http://www.preferredairparts.com/
Mr. Martin has a extensive list and outline which is very well constructed concerning the purchase of C337 parts.
Here-
http://www.skymasterus.com/
Good luck with your aircraft.