This is a hanger for helmets, and should work for both bicycle and motorcycle/racing helmets.

I printed mine in PETG and affixed it with 3M 30-lb outdoor mounting tape. I found that 15-lb indoor mounting tape failed after about two weeks holding up my motorcycle helmet, but might be sufficient for lighter bicycle helmets. Your mileage may vary here depending on the surface on which you're mounting this.

PETG or ABS are necessary for motorcycle helmet. PLA should be fine for a bicycle helmet.

UPDATE 10/17/2024: Added a version with screw holes