Sleeve for P6139B Passive Probe

I'm looking for the black sleeve/barrel that is under the probe hook (covers the probe barrel) for 500 MHz Passive Probes P6139B.

I believe you are looking for the insulator sleeve, part number 204-1226-01. This can be seen in the user manual under Replacing the Probe Tip: https://www.tek.com/en/passive-probe-manual/p6139b-p5050b. Take a look at the image in the user manual and let me know if this is not the correct part.