I have an old Lenovo X220 with removable battery. Unfortunately the mobile carriers shut down the whole US 3G network (or at least around here) with hardly any

I have an old Lenovo X220 with removable battery. Unfortunately the mobile carriers shut down the whole US 3G network (or at least around here) with hardly anyone batting an eye, so now my old phones are effectively bricked. I grimaced and got a Moto phone with an integrated battery, but made sure that replacing it is not too hard. Replacement cells are not too expensive, and swapping packs is a matter of taking out a bunch of tiny little screws and putting them back in, but no messing around with insanely fiddly and breakable connectors like (some) iphones have. I have played with the idea of 3d-printing a replacement back for some other phone, just to be able to use standard batteries (18650 or whatever) in it.