I went through this when I got Midnight Sun a few years ago. The shore power cable was rather stiff not to mention disgusting (whoever thought a white power cord was a good idea should be shot!) which does not float my boat.

Since I prefer to have a permanent dock cord that remains at my dock all season and a 65' unit on board for travel, it was a good solution for me to buy 100' of bulk and end plugs to make my own 2 cords to my desired length. After lots of research, I went with 6/4 SEOOW type cord and installed marine plugs as required. By far the most cost effective, lightest and easiest to handle solution as opposed to standard off the shelf marine cords.
Note that 6 gauge is standard for 50a marine shore power cables and rated at 55a when using less than 3 current carrying wires such as in 50a applications for boats.
SEOOW specs. https://rexel-cdn.com/products/coleman- ... 5396A66C46