Trailer Wiring Hook Up Problem

[FNGDiscovery]

The flap that is raised so that you can insert the power cord from a trailer has broken. That flap is designed to hold the trailer wire in tight so brakes and turn signals work. Does anyone know where I can purchase just that plastic flap? The dealership said I need to buy the entire trailer hitch at about $1700 plus a 4 hour install charge! All I need is the plastic flap, or even the entire piece with the wiring pigtail. The dealership said they cannot sell anything separately. I hope someone can help me. Thanks, Dick