This is a functional button, designed to give radiation hazard vibe when sewn. Because of this, printing in yellow and sewing it to yellow fabric with black thread will work the best, or do like I did and print in black and sew onto black fabric with yellow thread.

Use regular sewing machine thread and thin sewing needle, the slots are just 0.9mm wide. Make sure the printer does not overextrude or you'll have trouble pulling the needle through.

I include .step file in case you'd like to modify the model, and can add source FreeCAD project if requested.
The last photo has prototype buttons, possible prettier but sewn too close to the edges to be functional. I haven't saved their source files but still have gcodes.