Disneyshopping.com is selling the "Belle Deluxe" gown in red. It's marked down to $49.95 (was about $85.00 originally) plus I think as much as an additional 50% off. The princess dresses online aren't quite as nice as the ones they sell down at WDW, but they are still very pretty. I've ordered a few of them for my DD. They also sell the red cape and red accessories to match.
Hope you find what you are looking for.