I'm sure sorry to hear about the loss of your cord. I have been concerned about the same thing happening to my 50 amp cord. So I have made a few inquiries about the big yellow twist lock plug end that attaches to the trailer. About 5 different sources have that plug priced at $94 and up! My Heartland trailer dealer thought that was outrageous, as I also thought the same. He checked his pricing and found the same price area.
My goal was to make up a short cord that attaches to the trailer and can provide 30 amps, as most of the campgrounds we visit only have the 30 amp service anyhow. It seems to be a big risk (in terms of copper theft) to have the big cord plugged in and laying on the ground for the low lifes to see and easily take. So far I have not made the short converter cord because of the high cost of the trailer attach twist lock end. But does anyone have another way around this problem?? I suppose a guy could make up a 120 V cheater cord that plugs into an outside trailer outlet. But that cord would need to have both male ends, and that can be a deadly accident just waiting to happen. And that backfeeding of an outside circuit could have problems with the GFI, and at best would only supply 1/2 of the trailer's AC circuits, and be limited to a max of 15 amps. So I don't think that is any kind of a solution.
I did use a paint marker and put my name and home phone number on both ends of the big cord. Maybe that would give a entry level thief just a hint that he/she should steal someone else's cord instead. But that is about as good as attaching an ear tag to a calf that is about to be taken by cattle rustlers.
I hope someone has a better solution, and shares it with us.
Paul_in_MN