Carl at Race Supplies Direct does some, I originally did the design in 2006 when racing the 750SSie in Minitwins.
I sent him the measurements and in return he sent me a couple of sets.
Other DD guys use them often bought via his eBay shop
I had a text from him last Thursday as he is after someone to make him an exhaust for the DD bike he is building after JAC lt him down
He now has his new CNC machine in place so hopefully he will be back to making bits
Checkout the Desmo Due Paddock on Facebook