I purchased a flashlight (www.amazon.com/gp/product/B097DPZ2CL/) and a hip pack (www.amazon.com/gp/product/B00NXCK0XO/) and designed a clip to allow the flashlight to be carried on the outside of the pack. It's all parametric so you can adjust it for other uses.

This is version 2 of the clip. Version 1 would have worked perfectly if I wanted to glue it in place or if it wasn't situated so that I sit on it - it worked itself off of the strapping on the side of the pack. I still posted it because it would have worked just fine on the other side of the pack or if I wore the pack differently. Version one is available at https://www.printables.com/model/397461-parametric-flashlight-holder-for-shoulderhip-pack-

This version has a small lip to better secure it to the strapping. It's more difficult to slide into place because of it but is more secure. It hasn't come off at all even when I sit on the side of the pack.