Find an electrical supply house, I doubt you'll find it anywhere else. I used to use the stuff to repair commercial cooking equipment in college. The product I used was for very high temp areas and had fiberglass cloth insulation instead of plastic (though I saw plastic high temp insulation as well). It looked silver instead of copper though I am not sure what it was actually made of. As for the size, go back with what come out of the unit assuming it was original. Otherwise, do the math and size accordingly.
Tom
