Where can I buy a dress for 6th grade Homecoming?

Well we are having a Homecoming in about 3 or 4 weeks and I need a dress. Nothing too long , and really girly and fluffy. Just like a short looking tutu dress that would be appropriate for my age. (I'm 11) I asked my teacher if it was a Casual Wear Homecoming or like Fancy Dressy Homecoming and she said that it was a fancy homecoming. I don't wanna go there wearing an outfit I would wear to school on a normal day espically if its a fancy homecoming. I'm also one of the nominations for Homecoming Queen so I don't wanna look plain (: Please don't give me a site for dresses for proms that are 100$ something not too expensive but nothing too cheap . . . ! Thanks yhaa :)