Repairing a PS/2 mini-DIN connection w/o clock pulses
Examination of a female port details that it connects to one of the NC pins of the mini-DIN format, thus I am coming to the conclusion that the off-the-shelf PS2 replacement cable does not cater a connection for this pin. Does that sound rational?


"NC" in a pinout most often means "not connected" or "no connection."

It's fairly common for cable manufacturers to exclude wires for NC pins to save cost, so your assessment seems completely rational. 

You will have to find a replacement cable that specifically lists being fully populated. Worst case you can get some connectors, sacrifice an old Cat5 Ethernet cable, and roll our own. 

EDIT:

Did some research and found a few vendors that at least appear to have fully shielded cables with all 6 pins wired through.

Kray Cables on Amazon carries 1ft, 6ft, and 10ft cables as well as extensions. 

Digikey also carries at least one that has a mechanical drawing with wire color assignments for every pin.