Check out the Trek Earl it fits in your range and is a pretty basic steel framed single speed and it looks good and not that attractive. You can also take a look at the aluminum District S which goes a little over your budget but can be used in bad weather a little more as salt and water won't corrode the frame. People say that aluminum frames can crack but I don't think its a big issue with Trek or other quality companies and they offer a lifetime warrantee to the original owner of all their frames. Bicycle Habitat in Soho should have them avalible to test and their prices are usually pretty decent and they will most likely price match if you find it cheaper elsewhere.