Camco Heavy-Duty 50-Amp RV Extension Cord | Features Power Grip Handles, Copper 6/3 + 8/1-Gauge Wires, and Rated for 125/250 volts/12,500 watts | 30-foot, Used ONE season.
$30. in Kerrville, TX
Be aware of where and how you hook up the 12v line. In it's original configuration there should be some kind of isolation device that turns off the power on the line when the engine is not charging to prevent the house battery system from discharging the engine battery and leaving you stranded.
Can't say that I know first hand as I am not quite that old, but I can see that rv camping has come a long way from what it once was. When it was warm, everyone sat outside or took a walk around the park to see whats new. Much more sociable and connected with each other in person I would say. Then came air conditioning and it's been all down hill since then.