I'm looking for the trailering harness that plugs into the connector inside left frame rail.
the male plug is really all I need because I am wiring up a custom trailer plug. All the parts I see for sale have the factory style 7-way end on them and I don't need (want to pay for) that.
Truck is a 2002 F250.
Here is a pic of the plug I need:

 

have you tried etrailer.com?

 

Yes, but they just sell the whole harness. For what I'm looking to do, all I need is the connector on the frame end and I am building my own harness from there.