Fitting Into Dresses!!!!

Hey you guys-

I`m flying to Mexico on the Thanksgiving weekend and need to find a quinceañera dress in a few days. I was reading a post and it said they found a quinceañera dress in a size 4. Well I`m not skinny at all. I`m like 5`2`` , weigh somewhere between 130-135 and a size 9, so are there dresses of all sizes? or do you have to order the one you like and they make it in your size? It`s cuz I don`t think I`ll have time and I don`t want to have to choose one that I don`t really like. HELP! or how could I loose weight? It`s in a month!