Find me the perfect dress!?

Alright so I have a challenge for all of you guys. My friend Lizzie is looking for the perfect dress for prom, and we are having a little trouble finding it online. She wants it to be: strapless, criss cross back (corset-like) but the strings can't have fabric behind them! Like, open back behind them. Full length, formal, and either red or blue. We've been trying, and we just can't find one similar to that! Can you guys help her? (: