Comment by Rediscover

The NITECORE UM10 is an "in/out" charger too - it handles various sized LiIon batteries one-at-a-time. A switch on the end determines if it is charging or discharging. Their site says it's discontinued, but I thought I recently saw them at a shop in Seattle. Time to pick up a spare.

https://charger.nitecore.com/product/um10