Are there any good women's clothing stores in NYC's Financial district where I can get a cocktail dress?

I need a cocktail dress for a benefit tonight but I only have a 1/2 hour lunch and can't really leave the Water Street area. Cheap is better-is there something like a Forever 21 nearby?
I don't have time to do serious shopping and I'm just looking for a cheap, throwaway dress - this is a last minute thing

There's Century 21 right across the street from ground zero. Would that be a feasible option?

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