The Fluke 80k-40 40kV probe is for measuring voltages up to 40kV. It is for use with an AC/DC voltmeter or DMM. It has high accuracy when the voltmeter or DMM has an input impedenance of 10M ohm +/- 1% but can work with other impedances (you just have to do more work). Luckily my voltmeter meets this very requirement.

Supplier

It's made by Fluke but I purchased it from a local electronics store. It shouldn't be hard to find as Fluke is one of the biggest name brands you find in these stores.

The probe connected to my voltmeter. Note the ground wire with the alligator clip on the end.

Close-up of the handle so you can read the writing.