Best bobtail I have seen for the price is the Dan Wesson, not cheap though. If you want a cheaper bobtail, you need to get a RIA and see if a gunsmith will do it for you, a real gunsmith not just any gunsmith.
Of course by the time you buy the parts and the smith does the work you're still not gonna be in the cheap area. When it comes to a "custom" styled 1911 cheap goes out the window.
Just curious are you wanting a bobtail for looks, just to have one, or trying to make the gun easier to conceal. I have a small frame so a 1911 or any near full size gun is hard for me to hide easily.
If going with a bobtail, I wouldn't limit myself to a commander personally. I like the full size when shooting the little extra barrel goes a long way in accuracy, recoil (2nd shot), and getting a better powder burn (longer range).