This rounded L bracket has countersunk holes for the screws at each side and is easily customizable to your needs. Both sides can be customized with different length, hole sizes and countersink. Outer edge clearance and extra material at inner edge for increased robustness can also be adjusted.

If you just want a small standard bracket with 3mm or 4mm countersunk holes without special customizing, you can also use the attached customized sample brackets.

You have never customized a thing? Don't worry, I optimized this thing for easy customization. You can: a) Go to "Customize" on this page (directly below the picture) and start the Thingiverse online customizer OR b) Follow the instructions in the last picture, install OpenSCAD (only 50MB) and customize it with a few clicks there (helps to avoid the waiting time after each parameter change of online customizer)