I know this is an old thread and there is at least one other with the same question.
I think I might have stumbled on something today, check out (Google for) Pollack 11-933p.
No guaranty, I haven't looked really close, but I saw something VERY much like this on the back of a new McCormick a couple of weeks ago and nearly asked the dealer's parts guy to get me "that bit".
BTW, I first saw it listed as a Chrysler part and since I have a Dodge Durango I will probably squirm under there, trace back from the 7 pin trailer socket and see if I can pull out a short section that kinda/sorta looks like this.
Then see if it plugs into the back of the tractor.
Then explain to SWMBO (she who must be obeyed) why she can't pull a horse trailer for a few days (-: