Custom Prom Dress Designer For A Resonable Price

Is there a designer out there who can custom make my prom dress of my design for a resonable price? and plus i have a twin sister and she wants hers custom made as well and we really need a resonable price since our parents are paying for it..... I perfer someone from Chicago since thats where i live but if not then thats ok.... But if there is a dsigner out there PLEASE let me know