This is where you'll find all USB Powered Battery Chargers! Some have Micro USB and some have Type-C USB inputs, but all of them are really cost effective and often compact products.
Please note: you'll need an appropriate output from your wall to charge as quickly as these products advertise. If you plan to charge these off your laptop or computers ports, they may not be able to fast charge due to the amount of amps these USB ports can provide. We recommend 2A of output to be supplied to your charger; but don't worry, they're all smart enough to only supply what the battery needs.
Need an AC Mains Powered Charger? Head over here.