B.C.
This reminds me too much of JonBenet Ramsey. I realize some people have fun with beauty pageants. From what I've read, the kind of costumes you are looking for are expensive. Try looking at flower girl dresses for weddings. A Halloween princess costume is not going to cut it in a competition. I'd go for a Shirley Temple look rather than the 4 yr old Hollywood bombshell. Just my opinion, but a sexy look on a 4 yr old is just wrong.
http://www.sosweetboutique.com