Bill,
Guns
manufactured in Scotland will all be high end products, not repetition machined for the mass market. They will therefore be "expensive." Guns
sold in Scotland will be more or less typical of the rest of the UK, though in country districts they tend to be somewhat lower in price, at least in the second hand market.
Virtually all small towns in Scotland will have a gun shop of some sorts even if it's just an adjunct to the angling shop. You'll be able to buy cartridges and everyday guns. Here is a link to those non existent (some 50 odd, there will be more)
GUN SHOPS Across the UK shotguns can only be lawfully held on a Shotgun Certificate; there is no such thing as a special permit for hunting, farming, clay shooting or vermin control. You buy the Certificate, then the guns, record your purchases, and go on your way.
Probably the most commonly seen gun in Scotland is a Beretta O/U, just the same as everywhere else.
The advice to start enquiries in the village pub is the best way to go. You may not find the answers to your questions, but you will certainly be entertained.
Asking a passing Scot if he's common may not have the outcome you or your son anticipate. The reply could well be uncommonly warm.
Eug