Amazon.com: Oyviny 4-Way Flat to 7-Way Round Blade and 4 Way Trailer Wiring Harness Adapter Vehicle-Side 4 Pin to Trailer-Side 7 Pin and 4 Pin Dual-Output Connector with Mounting Bracket for Truck
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MICTUNING Trailer RV Boat Adapter 7 Way to 4 Way & 5 Way Plug 12V Flat Blade Plu | eBay
7-Way European Style Round Pin To 4-Flat Adapter
TowSmart 12 in., 4-Way Flat Trailer Wiring Connector 1441 - The Home Depot