Earlier quoted context omitted.
We switched to buying USB-rechargeable AA/AAA lithium ion batteries. The brand we buy is Pale Blue, but there are many other brands. These batteries have a regular form factor, with an added micro USB (and USB C on some larger battery sizes) port for recharging. They work really well for us and charge quickly (and conveniently — everything has a USB socket nowadays). The price may seem expensive, but after 10 or so c…
I wouldn't recommend this personally, having had bad experiences with poor charge circuitry in integrated chargers like these (in my case it was in a 18650 battery). Get a good charger (e.g. eneloop), and then you can get generic rechargeable batteries incredibly inexpensively for it, without risking poor charge management causing overheating or battery failure.
Or are you saying you can get 1.5V lithium rechargables that work with an external charger?