12 year old dress?

I am 12 years old and i need a dress for my friends bar mitzvah. I want it to be either red, gray, or black and not too expensive. I got some really cute black wedges but i dont have a dress but i could exchange the shoes. I need it by the 21st so it has to be a store i can go buy it at. please help me i cant find anything anywhere! i am usually an xs. i am 4'11 tall and i am really skinny. i have a normal bust for a 12 year old