I saw a couple cute ones at Dillard's the other day, however they were in the junior's department so only shorter/smaller girls could probably get away with them.
http://www.dillards.com/shop/Juniors...rs&storeId=301
^ Not all of those are suitable, remember to avoid prints or anything that isn't pure white! Also juniors is NOT for tall girls (not typically a fan of the jr's section after high school, but I know how difficult it can be to find a white dress)!