Chip McCormick came out with a high capacity frame in 1991 that was considered the shizzle for quite awhile for guys building guns for IPSC and other competitive shooting, but I see his company no longer offers it (although a few could be found knocking around somewhere, I'm sure.)
But it looks like Rock Island offers one now, and their frames seem to have a pretty good reputation as foundations for guys who like to build their own...
Here is one offered online:
http://www.gunbroker.com/Auction/Vie...Item=229886477