what clamps can you use to prevent the rear sway bar from sliding more towards the right/left?

 

whoa, I don't know if its just me... but I think you're gonna need either a picture with a more elaborate question or a question with more details within it. Just off hand, I'm guessing the anti sway bar was designed to allowed it to slide/give a little to the left and right. But I'm just guessing...

 

As in YOU with your hands can move it left to right? Your sway bar is like a big spring, you shouldn't be able to flex it at all, only the the weight of your car should be able to move it around if any.

Yes, more details.