We have lots of these. The generic Li-ion charger that you can use as a back up or to replace the ones that came with your kit.
While these have very basic features, they are very affordable. Use these until you can save up for the better, more expensive chargers.
These chargers can charge a variety of 3.7v Li-ion battery sizes from 18350 to 18650 batteries.
Plugs directly at the wall