I live in Edinburgh, and keep looking at the paddle butt Scots rifles that are in the Scottish National Museum. They are all snaphaunces with full stocked swamped barrels with bores of around .36. They all tend to be quite short apart from one enormous specimen which is known as the "Bredalbane Gun" which was made in 1595 and is the oldest known example of a Scottish long gun. It was being used as the footrest of a trestle table in an old house..!
http://nms.scran.ac.uk/database/record.php?usi=000-100-000-826-C
Nobody makes anything like them and they are very rare. The Scots were not great riflemen, preferring Broadswords and pistols to long arms. There used to be a thriving pistol making trade in several Scottish towns such as Doune and Leith, but most of the market was destroyed following the 1745 rebellion. Pistol manufacture for the Scots regiments moved to Birmingham, England which also made dress pistols. At one time steel pistols were part of Traditional Highland Dress along with a long knife or Dirk. These days only the "Black Knife" worn in the top of the sock still remains..!
Following the Dunblane massacre in 1996, most firearms have been removed from Scottish Museums.
The Rifle Shoppe Scottish musket obviously uses an early flintlock with a transverse sear, but not the authentic Snaphaunce lock used on the original long guns. I suspect that scratch built would be the only way forward.. they are pretty angular designs, and use fruit wood for stocks, but barrels would be a challenge!