This is an endstop holder for the Mostly Printed CNC (MPCNC). There are other models out there (1, 2, 3), but none fit my particular microswitches.
This model is currently sized to the red-and-black Omron switches shown in the picture, but more generally, it can be easily adapted to ANY switches. There's a table of XY coordinates of hole positions you can edit. I didn't make this an actual customizer project because the customizer app doesn't have a good interface for putting in a list of coordinates, but it's easily to tweak by hand. The code is documented (see code screenshot).
(If you haven't used OpenSCAD, it will still be easy. Just load the code, mess with numbers, hit F5 to preview, F6 to render for real, then save as STL.)