Making molded rubber plugs/connectors

[Shelby68GT500]

Seems to me I recall seeing some sort of kit years ago that would allow you to make your own molded rubber plugs/connectors. This is an automotive application where I'm looking to make up replacement wiring harnesses. I can source all the correct wire, male and female pins, but can't seem to find anything online about doing this stuff DIY. All the connectors that I'm looking to make I already have (old) to use to make the mold, whether it be with clay, silly putty or whatever. Hoping that someone here might have some ideas on how to move forward with this.

 

[endoftheworld]

Utileplast. Also maplin sell the same thing under another name but not sure what it's called. It comes in small beads, melts in a cup of hot water, and sets to a hard plastic. Only thing is it melts again when hot so maybe not good in the engine compartment.

If you are pouring into a sealed mould then just use potting resin, it's cheaper.