For Makita 40V XGT Lithium Battery Adapter w/Switch for Power Wheels upgrade DIY | eBay
Portable Power Source w/Dual USB & DC Ports for Makita 40V XGT Battery - Powuse
FERREX ALDI ACTIV ENERGY 20/40V battery adapter for MAKITA LXT 18V powertools | eBay
Makita USA - Product Details -DC40RA
Amazon.com: Power Wheel Adapter with Fuse & Switch, Secure Battery Adapter for Makita 18V Lithium Battery, with 12 Gauge Wire, Good Power Convertor for DIY Ride On Truck, Robotics, RC Toys and
Someone dug around Makita's new patents, found a 2x18V to 40V adapter : r/Tools