Quite quick to print support that allows you to attach a light to the back of a helmet. I use it with a light that clips into the notch made on this support.

To attach it to a helmet you actually have to use two clamps which will pass through the vents of the helmet then under the base to attach to the two end locations. A rather simple but effective assembly (I use it with an electric skateboard so quite a bit of vibration) and it hasn't moved an inch.