Hate to burst your bubble, but as you've pretty much figured out by now, the models sold at the big box stores sell them by wheel size and not frame size. It keeps the costs down by using the OSFM, which they claim is One Size Fits Most, but in reality it is One Size Fits...Maybe.

With your budget, you're going to have to go used. Look for models from Manhattan/KHS, Giant, Felt... just about every brand has some sort of offering in the cruiser segment.

Another option to consider- and only bring up due to your budget- is look at what BD has that might work for you. http://www.bikesdirect.com/products/cruiser_bikes.htm