Summary

The cheapest and best way to mount a light to your bike!

From https://www.arsenalproducts.com/3d-printing

Instructions

First:
Print 2 of these and mount one on top of the other on anything round on your bicycle. Fasten with a few zip ties (or even rubber bands) as shown in the pics.

Second:
Go find the cheapest LED flashlight that you can and strap it to the top. I've seen LED flashlights at the grocery store and pharmacy for less than $3. Voila!

Last:
I am always working on new stuff to print. If you interested in being the first to know when I release something new, then check out https://www.arsenalproducts.com/3d-printing

Universal Bike Light Mount