Where can I buy teeth whitening gel/beach that I can use with braces?

Most teeth whitening treatment I've seen requires the special mouth trays but I don't think this will work because I have braces? A gel that I can just put on the teeth would be good. Any tips?
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I prefer Listerine gel whitening strips. You don't need a mouth piece; they just stick over your teeth and dissolve. You can buy Listerine Teeth Whitening strips cheap on eBay at http://rover.ebay.com/rover/1/711-53200-…
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