My 3D printer is in a bit of a dark corner of the room. I wanted to be able to have a little more light available when I needed it, and don't have the space to simply install a lamp. I have several of the freebie LED lights from Harbor Freight lying around (https://www.harborfreight.com/2-piece-3-12-in-led-mini-flashlight-63600.html), so I thought I could make up a clip that would hold the light at the top of my Ender 3. The clip should be able to hold just about any flashlight that has a barrel diameter of 1 inch (~25mm for you metric users). The square side is 20mm.
Snap the square section on the aluminum channel and then snap the light into the round section. Voila! A little more light at the printer.
The square side that clips on the aluminum channel is a bit of a tight fit, but within a minute, I had it clipped on and shining brightly. I just have to remember to turn it off when I am done working at the printer. Batteries don't last forever, apparently.
Also, if printing a rather tall object, you might want to remove the light from the clip before the print gets tall enough that the light would interfere with the Bowden tube.
I used PLA, but I imagine any rigid filament would work. I printed it so the supports were under and within the square section. The supports separated nicely and the clip snapped right on.