Marinco is the "gold standard" for detachable power cords. It's almost all that you'll find in the marine industry.
Here is the Amazon link to the RV kit:
https://www.amazon.com/ParkPower-Mar.../dp/B000NUYZQC
There are several "other brand" kits on the market, some much cheaper (in price and with questionable quality). I can't say whether they are reliable or not, but I can definitely vouch for the quality of my Marinco kit that I installed in 2013 and have has no problems with it since installing.
https://www.amazon.com/Leisure-Cords...E51YQ7GZEK073E
https://www.amazon.com/X-Haibei-Inle...VKZHEC2X4YEST6