Update: Sold out, sorry!
Anker teamed up with Nintendo to make Switch-branded USB-C battery packs last year, and while our typical position is that there’s nothing special about them, you should absolutely buy one today.
For some reason, the PowerCore 13400 battery is marked down to $17, compared to the previous all-time low price of <checks notes> $50. It’s shipped and sold by Amazon directly, not a sketchy third party, but I wouldn’t expect it to last long.
For comparison’s sake, the larger version of the battery is also “on sale” right now for $70.