If only you could touch your ceiling. Because there is a cheap thing you could that would work seriously well for you. Actuly... you might be able to work around it...
Well, if you want to try it figure out how it could for you, maybe I'll give you the basic layout. All you need is a couple plastic bags, an 'eye' hook (in the orginal), a length of cord, and either a soccer ball or a basketball. Put the ball in 3-4 bags (helps to prevent it from just flying out after the first couple of hits), tie the cord to the handles. Tie the other end to the 'eye' hook, and screw it into the ceiling. This isn't exactly a heavy bag, but it is a good way to train reaction striking to a moving target.
You could probably rig it so it'll hang from the wall. Like with a speed bag stand.
Good luck man, let us know how this works out for you