Welcome to the site, Steve. Here are a couple of URL's I found to sites that have massive inventories of salvaged rv's for parts. I haven't used them yet, so can't comment on their service, prices, etc., but if you use them, please let us know how it went.
Also, here's a directory I found on rvescorner.com that has a very extensive list of salvage and surplus outlets.
Best wishes with your search.