Not sure the rings I've seen are REAL Disney wedding rings, but I've seen some really nice Disney rings that would work as wedding rings in the World of Disney shop in Downtown Disney...back in the jewelry room, which is kinda in the center back of the store. I've also seen some nice rings at the various gift shops in the resorts...Contemporary, Grand Floridian, Yacht Club...those come to mind. Another place that might have something is the MouseGears store in Epcot, where they have some better quality jewelry...look for the watches. I've also found nice pieces in the jewelry store in MGM. I can't recall the name, but if you are leaving Beauty and the Beast show, go to the shop on the right and keep going through...past the sports stuff. (Or if you're starting from the main street, taking the right toward Tower of Terror, go in the first gift shop on the corner and keep walking through the connecting shops...you'll come to the jewelry.)
Hope that helps!