It may be best to get a good one from a wrecker and graft new sections onto the rot. 1" strip and a union twist in the wire. Silver Solder and a 1,200 degree iron. FLOW it in there. Use a 3M product "self-sealing silicone wrap" it is used for field repairs on high power lines. Stretch it til it just about tears and wrap your wires tightly. As it heats and ages it melts together and forms a tough, conformal coating.

Stuff it in a split loom and tie wrap it up.