Awhile back I was splicing some cable that had been torn up by an excavator. After doing the splices I used shrink tubing and a heat gun to reinsulate them. It dawned on me that it might be worth throwing a short piece into my pack.
Last weekend I broke a tent pole out so made a internal splint out of forest products and slipped a piece of shrink tube over it and heated it with a bic.
This stuff comes in all diameters and will cover quite a range at that, like quarter inch to five-eights. Keep it just out of the flame and roll it around a bit. There is also some that has silicone in it for waterproofing.
The other great electrical product are zip ties, not much of a secret there.
Both weigh almost nothing.
When I got home I cut the shrink off with a razor put an external repair splint on it and then re-shrink tubed it.