Basic Pic rail mount for 24mm and 25mm handheld flashlights (measured around the barrel). The texture inside is good at gripping the stippling thats on a lot of lights.

Mounts to rail with M5 screw and nut

Im printing in PLA+ for now, but I believe that PETG, PC, or a blend of the two will ultimately be the correct material. PLA will deform and break, as this print needs to flex to put the flashlight in and and take it out of the mount.

I'm also including the model I made specifically for my Klarus XT11X. Adding a ring or two in the right place for your light dramatically increases the stability in the mount.