It might be we are both right, you are looking for an adapter that fits onto the treaded section with bolt holes for a regular bolt on six bolt disc.
This is one of the hubs with a cover for use without disc.
Maybe contact SRAM to see if they have any kicking about?
Let us know if you find...
Googling shows the brake itself to be very similar to a Grimeca System 8, obviously the disc mounting may be different.
For the price of those discs on eBay, I’d be inclined to confirm the central threaded diameter and maybe try one.
https://www.mtbr.com/threads/sram-9-0-disc-brakes.520555/
I believe the alloy bits that stick out are to space the disc out from the body, not where it fits on to. The inner face of the calliper would hit the wheel otherwise. The disc screws on to the thread section.
Only way it would work is if the disc was then staggered out towards the frame and...