I have a plotter/cutter that can do it, if it's under 0.08" thick.http://knkusa.com/shop/knk-zing/
You'd have to pay shipping both ways, but I'd be willing to give it a try. No guarantees, of course.
I just traced a circle and cut it with an x-acto knife. Made it slightly smaller than the hole and stretched it over the threads on the heating element.
You know that good old silicone aquarium sealant cures to something that is silicone for all intents and purposes. Why not just use that?