The local craft store has something called "Sculpey", that is a polymer
modeling clay.

Its a modeling clay that hardens when heated in a conventional oven to
about 275 farenheit.

I've used it with a lot of success to make strain relief's for
SMA-to-BNC adapters for my VX-5r handie.

I just never liked the teeny SMA adapters.

I don't know what sort of voltages this stuff might handle, nor how it
would weather--but it's easy to work.

example:
http://www.polymerclayexpress.com/sculpey.html

73
kaz