I've got the same problem, and unfortunately, no solution yet.
I did find an aftermarket camera w/30 feet of cord (unsure of exact length, but that sounds right) that would have plugged right into my previous vehicle (2011 Ford F350). Made for those like plow trucks, sand spreaders, which explains the extra length of cord.
What I don't know is if the plug on my Ram is the same as the plug on my previous Ford.
I'd surely furnish a link, but appears I have lost it.
The Mad Norsky, Doll, Logan and Rocky
2014 Ram 3500 w/ Cummins/Aisin
2019 Northern Lite 10-2 EX CD LE Wet Bath
RV'ing since 1991
I took the road less traveled .....Now I'm Lost!