Dow corning 1540-20p is a pourable silicone that can be formed in a mold any shape. Mix it with alumina or other insulator dust and you have a tailor made insulator with a lot of flex, insulating properties thermal capabilities, its off the shelf and inexpensive. 1 mold can make as many as you need and can easily be modified. Samples are easily obtained and would most likely cover the first few trials.
