Here is a manufacturer of the equipment used by Airstream with a link to the 50 ampstuff.
Furrion Store | Electrical | Power Cordsets
I have used many variations of their pigtails and cables.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC
TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels