A have a rather large dog and rather large dogs make rather large poops. Since Doggo gets walked three times a day including once at midnight I often have to walk the dog in the middle of the night and the dog seems to like the pick the darkest sections of the neighborhood to do his business.
So I bought an el cheapo dog poo bag holder with a flashlight built in. It was nice but within a week it was broken. I later ordered a pair of them from Amazon, one of which did not hold together. Finally I had enough and decided to make my own out of PLA and putting the guts from the flashlight part in the end well. The result seems to be fairly strong, definitely better than the thing I am replacing.
This is version one. If you find it useful, feel free to use it or remix it.