How to connect a 4-wire to a 3-wire outlet - Quora
Nema 14-30P Cord Plug for 4-wire 240v, 30 amps
Amazon.com: Nilight 4Pin Way Electrical Wire Connector 10 Pack 16AWG Male Female Plug Socket Quick Disconnect Waterproof Plug Play 1.5mm Series Terminal for Car Truck Motorcycle Marine Boat, 2 Years Warranty :
CURT 4-Way Flat Connector Plug with 12" Wires (Trailer Side) 58030 - The Home Depot