David Travallian shows how it's done in the book Shotgun Technicana.

If you're not inclined to do it yourself, I'm sure there are a good number of smiths here that can help you out. Steve Bertram, possibly Mark Larson, Classic Gunstocks, Dennis Potter, CJO, Gunter Pfrommer, and others that I can't recall at this time. Each would have their own quote. Best to contact one of them directly and offline, IMO.