This is a 21 mm diameter cap that I designed and printed to replace ones that we lost while working on my sister's 2018 full size Transit van. I explored creating my own tessellation to mimic the textured pattern of the original cap. It worked out pretty well. The Transit van has a large plastic step at the sliding door opening. That step is held down by three or four screws that are then covered with these little pop-off caps.

Print instructions

Printer Brand: Prusa
Printer: I3 MK3S
Rafts: No
Supports: No
Resolution: 0.1 mm
Infill: 15%
Filament: Prusament PETG Black
Notes:

Inverting this in your slicer (pattern face-down) should allow you to print it with no supports. I think I even printed it right-side up without supports. Higher resolution yields better texture results, although the nature of the print is such that just about anything will look good in this application.