Betsey johnson/heatherette-like party dress; where to find one?

i'm looking for a party dress to wear to prom that has that rockabilly/whimsical/vintage/teaparty kind of feel to it. light pastels, ruffles, tulle, short skirt, and all that good stuff. i'm planning to wear black booties with it. my budget is $200. where can i find one online?