Yep, any 18650 battery will do the trick.
They come in "protected" and "unprotected" varieties; this one is "protected", meaning it has a wee circuit that keeps things from getting burny and explody if something goes wrong. You definitely want protected for this light.
You can get high-quality, higher-capacity Panasonic, Samsung, LG, etc. batteries from many different sources, and the light will last longer.
However, fake Chinese cells are all over the place and hard to avoid on Amazon or fleaBay. Stick with a reputable supplier that can verify authenticity of the brand you're buying.
People who are into vaping are absolutely obsessive about these cells. Your light isn't that demanding, so any decent cell will do just fine; you don't need to spend a lot.
Locally, I'd stop by the local vape shop, found on any strip mall or corner, and they'll set you up with a few cells and maybe a charger.
On t'intarwebs, I'm not sure what's the most reputable shop nowadays, so I'll let someone else answer that.