Richard - the whole point of mica is that it combines being an electrical insulator with heat resistance. A different sort of washer is likely to be more dangerous rather than less.http://en.wikipedia.org/wiki/Mica#Electronics.
That said, we used to have a flip down toaster, and I always liked the toast it produced, even the thick things where I had to stand there holding the handles to keep the door closed until it was done.
Quack!
GtD.