I have a headlamp for hiking with a slightly different take on this.
It will take 3x ordinary or rechargeable cells, or it will take it's Li-Ion pack that is the same size as the 3 cells side by side. Designed in from the start so there are no dangerous bits. Hiking headlamps are something where you do *not* want to be left with a dead battery!
A headlamp that can run on either AA or 14500 tends to be a better approach than this. Those proprietary batteries are usually pretty expensive compared to a 14500, and three AAAs as spares aren't nearly as convenient as one AA.
There are a handful of these on the market and they're not common in retail stores. I'm fond of the Skilhunt H150.
It will take 3x ordinary or rechargeable cells, or it will take it's Li-Ion pack that is the same size as the 3 cells side by side. Designed in from the start so there are no dangerous bits. Hiking headlamps are something where you do *not* want to be left with a dead battery!