You can blame Bosch for this, but the connecter on the Hall effect bean can models (and on the Ignition Amplifier) is NOT an automotive part.
Bosch wanted something that was weather proof so they looked to industrial control equipment and, believe it or not, domestic appliances.
The strange plug/socket combo is called "Junior Power Timer" (and no I have not been at "certain substances", I am quite serious).
They are available from specialty electronic suppliers, Farnalls and RS-online have them. I purchased 5 sets on eBay from a guy in Switzerland.
If you manage to smash the housings in the process of pulling them apart you could simply replace them with a simple 3-way AMP type plug socket, or even a later modern automotive waterproof connector, but if you do decide to buy new JPT housings the good news is that the JPT was so tightly defined that the "prongs" you have soldered to the ends of your wires will fit the new housings.
As far as the tester goes I frankly think it is a bit of a solution looking for a problem unless you are going to commence wholesale repair of bean cans. I find that a 9v battery and my multi-tester, with a couple of alligator test leads takes around 10 secs to set up and will quickly tell me if a beancan is dead or not.
For what it is worth I have located a Chinese manufacturer who claims to be making mil-spec (and licenced) Honeywell 2AV54 copies. I have requested a sample and that they prove out I shall buy 100 or so and become rich selling them on eBay. (You heard it here first).
