Very simple Hex Key (Allen Key) bracket. Feel free to edit the shape and hole sizes in the OpenSCAD sourcecode.
Most parameters could be easily changed by modifying the variables at the beginning of the scad file. Try it out!
Unfortunately I used the wrong search tags here on thingiverse and did not find a hex bracket, so I made one. Later I fond that there are a ton of hex brackets on thingiverse, but feel free to print mine anyways if you like it.