Your Lance dealer should be able to furnish a factory mads "jumper cable" assembly that will do just what you need.
My dealer in Ham Lake, MN had just the thing and wired mine up in nothing flat, while at the same time incorporating heavy gage hot and ground wires such as the Lance female end on your camper already has, direct to the engine compartment for the hot wire and direct to the truck chassis for the ground. I'm sure they could supply you with the needed harness extension.
I do not think the OEM wire circuit has a heavy enough wire to support fridge use direct from the vehicle wiring circuitry if you plan on using the fridge on 12V while on the road.
