There are none that I know of. Jim West (Wild West Guns) is better known as a pistol smith and rifle smith than a double gun smithy, other than that, there is slim pickens. There are more gunsmiths up there that specialize in rifles and pistols than shotguns. Great Northern Guns has a selection of doubleguns, but no smith that I'm aware of. When I was up there...it was a matter of boxing the gun up, and sending it down to the lower 48 for a trusted smith to work on your gun.

Dustin