I generally do not make magical available in shops. Mostly, b/c with the way DC works, there's an infinite number available.
I have been thinking about trying something for my mod which will be a quest with a string of who pays events for magical items (not weapons).
I do remember a very early game of AD&D that I played as Manikus the Ranger. We were in a large city and were at a shop that sold magic items. There were two iron goelms on either side of the door, protective spells cast in the shop and several guards that individually could have taken our whole party out. Oh, and we couldn't even come close being able to afford the cheapest item.
