Europe To US Trailer Light Converter for European 7 pin to American 4 pin Adapter Wiring Connector Trailer Plug Accessories - AliExpress
4 Way 4 Pin Flat to 7 Way Blade 4 Way Female RV Style Trailer Truck Wiring Adapter Connector Kit Light Wire Plug Car Accessories - AliExpress
CURT Electrical Adapter (4-Way Flat Vehicle to 5-Way Flat Trailer) #57187 | Ron's Toy Shop, Inc.
Hopkins Towing Solution Nite-Glow 7 Blade to 4 Flat Adapter
Amazon.com: OPT7 7 Pin to 4 Pin Trailer Adapter with Secure Tab, 7 Way Blade to 4 Way Flat Trailer Light Adapter, Connecter for Trailer Tow Hitch and Redline LED Tailgate Light Bar : Automotive