One of the few I've read good things about the rebuilds from is Four Seasons.
I don't know who might carry them on eBay, but I did locate their parts on Amazon, and was surprised that they were at least reasonably priced, though not bargain basement cheap.
To find their part numbers, just use the catalog on the site, and then search the PN on amazon or ebay. Most don't seem to list the MB as an application on the ads, but it cross references on the manufacturer's site.
http://www.4s.com/Online%20Catalogs-eCatalog/Content.aspx