I believe in Waukeen's Promenade if you go to the Adventurer's Mart there is a lady between some bookshelves in the back who may sell one. Or maybe (again, in Waukeen's Promenade), if you go up the tiers just to the right hand side of the destruction from the battle between Irenicus and the Cowled Wizards there are two fat merchants up there somewhere (on the rising walls). One of them.
Between these three people you should find a scroll case.
The madness of being normal explains the rationality of going crazy Life is measured not by the breaths you take but by the moments that take your breath away
That's what I said, almost every merchant except temples that sell spell scrolls have a scroll case to sell.
Ribald has one, the magic chick in his shop sells one, the book merchant sells one, pretty sure Bernard sells one, the thief on the 2nd floor of Galen's house sells one, the Oghma scroll seller in the docks has 1, the chick at watcher's keep sells one (and a potion bag), that guy in Saradush sells one, I think the drow merchant in Ust'natha has one (it's been awhile).