Hi Paul, Try 'Dotmar' in Talavera Rd., North Ryde. Not sure if they will supply to the public tho. Mate of mine works at a Co. that uses heaps of diff. thickness's of TEFLON tapes/blocks/sheets etc etc........
Got some really thin stuff, (5/10/20? thou, sticky 1 side), off him to re-shim my r&p couple of years ago. Now I have zero slop + no image shift. Electric focuser is really smooooooth. np.
HTH.
L.
Googled >
http://www.dotmar.com.au/
>
http://www.ferret.com.au/Companies/Dotmar-EPP
>
http://www.ferret.com.au/articles/21/0c02bf21.asp