I have an old pigtail with the male end of the plug for the TPS & I wonder if anyone knows where I could buy a female plug to simulate the plug for the TPS so I could install this adaper inline with my TPS to set it with a voltmeter.

 

Why buy stuff when you can leave everything alone and push the leads from the meter into the back of the existing connector? Cheap and no tools/equipment required other than the meter.

 

I'd rather not take a chance on damaging the connector.
I can't believe the part I would need would cost more than a few dollars anyway.

 

Your looking for the sensor side of the connector? If so, and if you have a spare sensor, crack the casing off of the spare sensor and solder the wires from the pigtail to the appropriate lead. The only other thing I can think of is to get some automotive connector pins, crimp them onto your pigtail, and hand insert the leads into the engine harness.