Video of prototype: https://youtu.be/gbsthg5cwzg

Finished item: https://youtu.be/4b8INuYfqpU

Simple design with great off-the-print-bed flexibility. If a longer belt is needed than the print bed allows, you can clip together multiple copies end to end.

Design is parametric. Alter to your specifications in OpenSCAD, or use Customizer here for limited changes. I find Customizer very unreliable and prone to crashing, so I highly recommend trying out OpenSCAD. You don't need to be a programmer to use it. Just look for the variable you want to change, type in a new value, hit F5 to preview, F6 to render, and then the STL button to export.

For Customizer use, these are the hole types: 0 = nothing, just a plain band 1 = circular hole 2 = rectangular hole 3 = square hole 4 = inlaid circle 5 = inlaid rectangle 6 = inlaid square 7 = spikes 8 = inlaid text 9 = extruded text