Portable illumination
Rules:
Related:
I have not had to deal with this situation but I have a CR123A here and just tested it in a 18650 case and it fits fine enough that you could use one. With them being short you could carry two where a single 18650 goes. They will rattle around a bit.
If you're looking to carry more, Illumn has these here.
I don't have one of these lights, but from looking at reviews it seems like you should be able to lock it mechanically by unscrewing the head a quarter turn from the body, breaking the electrical connection entirely. Then you could leave the battery in the light. Seems safer and more convenient to me.
Should be able to fit in one of these cases: https://www.18650batterystore.com/collections/18650-battery-cases.
That said, can you just unscrew the tail a corner turn before putting it in your pocket.
You could put a slip of paper between the battery and the contact spring inside the light. New flashlights containing batteries are often shipped that way.
If you want to go fancier, Countycomm.com and Illumn.com both have various kinds of battery holders. Here are some particularly nice ones that are on the expensive side:
https://countycomm.com/products/delrin-aaa-battery-locker-waterproof
I have a couple of the countycomm delrin holders for 18650. I can vouch for both the quality and the cost. While pricey I haven't found/seen anything I like better. (3D print may be an option if you have a resource you can use)