So, I liked ssd's Parametric buckle. But I didn't think it was parametric enough. This isn't perfect, I don't think. But it is customizable.

Some settings are, obviously, broken. Meaning you can make the holes larger than the buckle itself. If you do, it won't end well. Caveat emptor.

Ignore the lack of good infill on the sample image. I need to readjust my extruder settings.