it looks like he either made the adapter himself or had it machined.
this is a google translation of the text at the bottom of the page:
Adapter rings for FSQ85 and reductor
The weight of STL11K is too important to take on the gearbox, I design rings to eliminate all constraints. With the sensor is mounted to the CCD is now fully covered. As you can see in this picture.
going by this chart though:
http://www.optcorp.com/pdf/Takahashi...ystemChart.pdf
all you should need is the reducer, CA35 and wide T mount