You want just the wrist, or the gripper too? How much weight? Is it going to sit on a desk or be at the end of an arm? Most of the DIY grippers use hobby RC servos.
I need an arm like the one on the iRobot Packbot EOD. Unfortunately they cost more money than I have and iRobot isn't going to tell me how to program it anyway. I was just doing a search for parts, since I do have money. I'd love to build, but there is no way I'd get it done.
It's amazing what you'll find on ebay as far as robotics parts. Some of the older robots are pretty much selling for scrap. I bought a very large GE welding robot for $125. And there are a lot of pneumatic parts too, if that's and option.