Nikko 9.6v battery pack and charger substitution set.
Make your own RC Car Battery Pack or Repair NIKKO Ni-Cd 6.0V-620mAh - YouTube
Nikko 9.6v Slide Slot in Battery - Etsy
Amazon.com: HQRP Compact Battery Pack NI-MH 9.6V 1200mAh Rechargeable with Standard Tamiya Connector for RC Car Boats Robots Hobby 4/5AA : Toys & Games