Well it's not full-frame, Todd, but I have a Kodak Pro Back for sale on ebay, here:http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190489738280&ssPageName=STRK:MESELX:IT#ht_500wt_1087
Photos and info there. Let me know if you'd like to talk more about it. It's a 16mp back, the most affordable back you can get for the Contax with that resolving power. I really like this back and have owned several copies; in fact I still own another one that I intend to keep. Difficult to find them complete, but this one is.
Probably should have listed it here first, but if you are interested I can pull it off ebay (since it is a "buy-it-now" sale).