I used to keep a charged spare on me.
There's at least one Chinese brand that has smartphone with hot-swappable battery: https://rugone.net/products/xever-8
Removable battery. Swap within 2 minutes for zero interruption. After 2 minutes, the device enters a 60-second safety lock-out to protect your data.
Unfortunately, software from these brands tends to be shit. I feel like they just outsource it to the cheapest company. Especially following this recent thing:
As of March 4, Sophos X-Intercept telemetry listed over 500 unique compromised Android devices across nearly 50 models. The devices were mostly low-cost models produced by the following manufacturers: Allview, BLU, Dcode, DOOGEE, Gigaset, Gionee, Lava, and Ulefone. The list did not include Alldocube devices, despite Kaspersky reportedly observing Keenadu affect that manufacturer as well.