Personally, I wouldn't bother.
I've never had a probe go out due to water (only fire)
even the original probes that are 5+ years old still work.
the trick is to not submerge them in water.
I was the probe itself with a semi-wet scrubby sponge. I scrub until its metal colored again. Then i wipe the probe and its cable down with a couple clorox wipes, then i store them in a little tupperware thing.
If you run everything under water, they're going to fail.
shrink tubing isn't going to save the day. the cable protector itself is woven, it will wick water very easily.