@trouble @ascentale @mossyfoot @bikenite I was asked what kind of battery. It's this one!

https://www.ebay.com/itm/186641137947

It's kind of a rare model but it is out there!

You'll need/want to take off the battery's included regulator circuit board; the MonkeyLight canister has its own. But that's easy, it's easy de-soldering.