Well I have some good news for you. There is actually a pretty large selection of plus size formal wear on the internet. Now I know it is hard to buy on the internet as you don’t know how the clothes will fit, how the color ill look, etc. however, I have another suggestion. I would use the internet as a resource to decide what kind of outfit you are looking for. There are actually a few really good plus size website devoted almost entirely to formal wear. It would seem that at least some people realized there was a market out there to take advantage of. Now look on the internet and you will find that there are actually some very nice flattering things for larger women. These pictures can be used a good templates to take with you when you go to the stores to look.
If you are a lot braver than me you can even just order the dresses online and then have any alternations made at home after you get the dress. I have to say I was surprised; there are some very nice things on these sites. I think that more women need to be made aware of what is out there.