Amazon.com: CARROFIX Trailer Wire Extension - 4 Way to 5 Way Flat Harness - Universal Adapter Connector 4 Pin to 5 Pin for Connecting Signal Lights from Truck to Boat Trailer and
MICTUNING Trailer RV Boat Adapter 7 Way to 4 Way 5 Way Plug
Reese Adapter 7 Way Round to 4 Way Flat in the Trailer Parts & Accessories department at Lowes.com
Reese Towpower Wiring Adapter, 7-way Round To 5-way and 4-way Flat in the Trailer Parts & Accessories department at Lowes.com