A simple model for round PIR sensors (e.g. round zigbee PIR sensors) This one needs 3 dowel pins at 3x16mm and no other hardware.

Also worth noting: The dowel pins allow this one to move and adjust a bit, to find the optimal angle. And complete assembly before mounting to your wall is possible thanks to the cutout in the arm.

For assembly to the wall a mounting screw is recommended. Their large, flat head (~13mm) make a secure fit and breakage of the 3D print less likely. A picture for reference is added.

Recommended print settings: PETG, ABS or ASA depending on use case (e.g. indoors, or outdoors?) 3-4 walls 3 top/bottom layers 25% infill