HI Graham. If you get stuck, have a chat to Kenneth Williams at Armstrong Energy. https://aecomponents.com.au  

Rather depends on how exotic the gasket is, but they can make most things seal / gasket/ bushing out of all sorts of materials. They can punch, print or machine most things. I did a lot of work with them in my power station days and can reverse engineer most consumable bits. Kenneth did come out and do a presentation at a monthly meeting a few years ago.   Andy

Tractors and industrial machinery  in Bayswater. They can make old type gaskets etc.  

Gaskets & Seals Australia Wide | Associated Gaskets (agaus.com.au)

Associated Gaskets welshpool could be a contender .  

Please let us know when you have had one made and details about it . 

cheers Todd