Amazon.com: Blomiky 2 Pack 6V 900mAh AA Battery Pack with JST Plug and USB Charger Cable Suitable for New Huina 540 Dump 520 RC Bulldozer and 510 Excavator 540 Battery 2 : Toys & Games
3 x AAA Battery Holder with On/Off Switch, JST, and Belt Clip : ID 3286 : $2.95 : Adafruit Industries, Unique & fun DIY electronics and kits