If you disconnect the wires you can simply remove the old covers and install new that is available on line or maybe at better auto parts stores. I was successful using heat shrink tube just big enough to slip over the plug connector, 1/4” or 5/16”, the applied the heat. Worked well.
To maintain originality you will need PVC sleeving. Electronic companies like Digikey sell it. Most people use heat shrink as it is easier to find. Neither one is particularly heat resistant.
Brian that is good to know. If you look at my photo, you can see the open portion closest to my hand. The wires & PVC cover were left between two of the head fins. I’m lucky it didn’t ruin the wires. I will see if I can find the PVC. If I can’t, I’ll just use heat shrink. I can always remove the bullet ends, run the wires through and terminate new bullets on the ends. Victor
If you fold one connector end back about 1/2" it makes the pair 'skinnier' to slide into the shrink tubing. Straighten it out afterward, before shrinking....