I don't know the first thing about the Pride of Scotland shop, but the Pride of Scotland tartan is actually a copyrighted and proprietary tartan of MacColls of Aberdeen. Unfortunately, it has been ripped off and mass produced by a number of different companies, which is why you can find it all over Ebay and elsewhere. Last I heard, MacColls were pretty actively trying to enforce their rights on this tartan and restrict all the unauthorized production of it, though I don't know how much luck they are having, as you can still see it for sale everywhere.