Have you tried Craigs List they usually have a good selection under bikes just a lot of looking. You need to know what size that you will want to have and what options and how much they cost so you don't get taken for a RIDE so to speak.
bikesdirect.com has a sizing chart for the bikes they sell. Note Bill H. and Junkman are correct that you need the right size bike. If you get a poor fit, then you will end up hating the bike.