Well, it turns out that a Seeed Xiao esp32 lora board fits exactly into the 18650 battery bank case from the dollar store. Added a 2500Mah cell, and RAK PCB internal antenna. Getting 14hrs from full charge to the cutoff, Bluetooth connected the whole time. I'm sure a NRF52 would fit just fine as well.
Bought one at a Dollarama in Carleton Place, and another at Giant Tiger (not a dollar store, but cheap store) in Arnprior. Ontario, Canada