CLAMPS!

This is a parametric clamp with a pad on the end of the screw that swivels and rotates. 

The OpenSCAD source code is included in case you want to customize it, but requires threadlib to compile. Please don't ask me how to set that up for you. That's what google's for. 

I've also included four STL files as examples.

Printing

The model is arranged so that it will print as-is. You shouldn't require any support material.

Assembly

There are three parts, the screw, the pad and the bracket.

Thread the screw partway into the bracket.

Attach the pad. This can be a bit tricky. It's a very tight fit, so you'll need to wiggle it into place while pushing on it. Worst case, you can always trim away a bit of the pad's opening. Once in place, it should stay on, but tilt and rotate freely.