I have 22 1977 RC Cola baseball flats up for auction (closing Sunday) on EBAY. These include several of the scarcer white flat variety.
Here is the link to a George Brett flat:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=110642746570
and a Yastrzemski flat:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=110642754939
You can obviously see the others by looking at my items for sale on EBAY.