An issue with several companies. No good fix. Tape is ugly & comes off leaving a gooey mess. Heatshrink is too stiff & can't get small enuff size over ends. Perhaps experiment with liquid rubber? But the rest of the cover is failing also
I think it's a common problem. I have a Simrad with a simple handset (just a mic with cannel and a speak buttons) and the insulation is also disappearing. I made a repair with vulcanizing tape but it just continues. Curious if the cables are custom or if you could find a replacement and have fun with a soldering iron and a screwdriver...
It's common, have two different icoms with the same issue. Icom did a recall swap on 802 mics for a year or so but I think it's still a issue. My guess is it's not a proprietary plug on it. I would take to a electronics place and see if they can replace the cable. You may end up with a non vulcanised plug bit it would have the same IP rating.
Looks like lots of replacement mic cables out there, I would stop by a local Ham radio place and have them take a look. I know the icom command mics are crazy expensive would guess simrad is the same. Probably get a cable for $20-30 plus instal.
Unless they are doing something wierd, like Garmin does and the cable construction is the same, IE conductors shield etc don't see why it couldn't get replaced. It may be soldered directly to a board in the handset but that's unlikely. Well worth stopping by a ham radio place or electronics shop to see what they think.