And while you may not be a vaper (I personally think it's a nasty habit to get hooked into), many vape shops carry 18650 batteries for vapers to use in their vape pens. It'd be a great option for getting some locally that are most likely known good batteries. I'd recommend not going as cheap as possible with these things, because the cheapest ones tend to be the counterfeits; keep in mind that you'll likely have them in a strap next to your head, and my thought is that I don't want to put something that's sketchy next to my noggin.