Last year I replaced the 18650 cell in my Cygolite.
I upped it from 2.2 Ah to 3.5Ah. The green one came out. The other blue one is a new 2.2Ah. I had kind of abused the cell by running the light in really cold weather, then plugging in a little external 10Ah pack with a USB to charge while it was running., Not nice to do in freezing weather, but hey - nobody got hurt.
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I ordered from Digikey
https://www.digikey.com/en/products/...rnTYArj1xjRooA

You need to match the voltage to the battery in your light. A higher amp-hour number means longer run time (and longer re-charge time...). The charger in the light takes a 5V input (USB is 5V). And a PC or wall-wart is going to limit the current to 1A or maybe 500mA. It'll say on the wall wart.
My new battery cell now let's my little Cygolite go much longer - as expected: MORE Amp-Hours!!
The new cell did require I cut the connector off and solder the leads to the leads in the light. The connectors just didnt match up.
--- Make sure you get the positive lead and the negative lead right! -- If you have a DC volt meter (or a friend who knows the difference between AC and DC....) you'll be good.
So if you know your voltage and cell size, you can search Digikey. Some of the cells you can buy have some kind fuse circuit on top of the battery - get that! A little extra protection so you don't burn down the campground.

If you're local to Detroit, we can probably arrange to meet so you can "buy" the unused 2.2Ah one I have. I don't think I want to deal with lying when I ship it.... (and by "buy", I mean swap for a cup of coffee.....)
As for me, I cannot get the idea of a Son Hub generator out of my head...... just got to get my wife to let the cash out of my wallet!! ha!

ciao