If it is just the outer cable covering that is disintegrating, and the conductors are still carrying all the signals needed to have complete functionality of the radio, why not wrap the cable in something? In effect, give it a new skin. Heat shrink, hockey tape, even electrical tape (yuck) come to mind, and they come in various colors. I wouldn't recommend black or a dark color, because of heat absorption, but this seems like a cheap fix if the problem is cosmetic and/or lack of protection for the conductors.