This clamp is based on the Carbide3d Essential clamp.  I needed a clamp that was a little bit longer.  The Fusion 360 model is parameterized so you can change the length if you want. The STL/3MF model is 5 mm longer than the original.  The slot is sized for M6 bolts.

It prints best with supports.  I used 4 perimeters for the vertical shell and 50% infill.  I recommend printing in PET-G