For your own use, you might be better off making a cable with the correct end on it, rather than trying to find something already made.
Mine I have what looks like a computer power cable that plugs into the NATO slave port in the truck. I think it's supposed to be for some type of battery charger assembly.
Something like one of these might be a good start; just take the end off the cable you already have and put it onto this:
Low profile Mini NATO Cable
graywacke.net
or if you don't want to disassemble that one, this thread has numbers for ordering the plug end and how to make one
Looking to wire up a RAK15 ration heater from scratch. Draws 24vdc 15 amps. 10 gauge directly from the batteries with 20 amp. inline fuse?
www.steelsoldiers.com