Hopkins Towing Solutions 6-Round to 7-Blade Adapter, CA Prop 65 Compliant, 47435 at Tractor Supply Co.
Amazon.com: CXTM 7 RV Blade to 6 Pole Round, 6 Way to 7 Way Adapter 7-Way Blade to 6-Way Round Trailer Adapter 7 pin to 6 pin Trailer Wiring Plug Adapter : Automotive
Curt 57003 7-Way RV Blade LED Electrical Adapter | U-Haul