Bergquist (now Henkel/Bergquist) manufactures an array of thermal management products. One of these, ¡°Silpads¡± is a product I have been using for replacement purposes. It is a flexible, rubbery material that many OEM manufacturers use instead of mica.
The neat thing about this product is that you don¡¯t need to apply any thermal compound. And it can be purchased from many distributors in the common shapes for transistor heatsinking, etc.
As for your application, you might try contacting the manufacturer to see if you might be able to obtain a small sample of a sheet to cut up and fit in the unit.
Greg
