I remember seeing some Stitch merchendise at MK in the gift shop by Alien Encounter too and I believe I saw some at MouseGears at EPCOT.
As for Belle, there is Princess toys everywhere at WDW. Tinker Bell's at MK, MouseGears at EPCOT, the shop by Little Mermaid and LA Cinema Storage (on the corner of Hollywood and Sunset Blvds), Once Upon A Toy and World of Disney at DTD, and one of the shops on Discovery Island at AK (can't remember which though) are usually good shops for Princess merchdise.