They make 26" BMX bikes for the cruiser class. They usually don't have front brakes though. You can get a SS mountain bike like a Redline Monocog that should do what you want. SE makes a couple also and you could check out bikes direct, they usually have a couple of cheap single speeds.
Edit... it looks like Redline doesn't make the Monocog in a 26 anymore. The 29 will jump, but it felt huge when I rode the BMX lines at Rays.