After trying out various designs for mounting a cheap LED flashlight from China to my handlebar I simply designed my own. I added STL files for handlebars with 22 and 25 mm.

For other diameters you simply have to adjust the OpenSCAD file, render and (re)export to STL. While the text in the file is German I guess you can figure it out yourself :-)

For mounting the flashlight I used a 20 mm wide Velcro fastener. Screws used were M4x25 mm. I printed in PETG with 100% Infill but less infill and a lest stable filament should work as well.

I typically buy something like this: https://de.aliexpress.com/item/32980156147.html

Be aware that any flashlight will severely blind other folks in traffic. So only use this either with the beam pointing direct in front of you or if you are outside the city.