The only ones I've seen are Lipsey's exclusives, with short tubes, lowered hammer spurs and are chambered in .45 ACP or .45 Colt. Here is a link:
http://www.lipseys.com/itemfinder.as...ero+Birds+Head
I have .357 SASS Edition New Vaqueros. My wife is sharing them for now but eventually will want her own revolvers. I'd like to get her a pair of .38-.357 revolvers with a birds head grip frame but Ruger is not making what I want.
The Cimarron (Pietta) Thunderball is similar but they are difficult to find.