This is what I came up with while researching the same thing.
The Cinderella Slipper dessert can be ordered at Cinderella's Royal Table in the Magic Kingdom, or at any of the table service restaurants at the Grand Floridian: 1900 Park Fare, Citricos, Narcoosee's, Victoria & Albert's, or the Grand Floridian Cafe. At any of these locations, you must order the slipper at least 48 hours in advance by calling 407-824-2578. Prices can change, but currently the slipper costs approximately $15.