That's the German DIN broadcast standard hub, used in many European studios.
[BTW, German is my mother's language, so feel free to ask.]
What tape recorder do you use?
The picture you refer to is for a Revox or Studer machine (PR99, A807,
The platters exist in two sizes: 10.5" and 12", depending on the machine.
On a regular Revox, you also need to change the reel hubs, unless they
already have the two additional holes and longer grip to fix the platters.
Any decent Studer or Revox dealer should be able to supply a pair of them
(or a complete set including the hubs).
It may be expensive to ship from Europe.
This store sells a lot of Studer and Revox gear:
Jos Van Dyck
NGM Archiving Solutions
Mechelen - Belgium
> Just what I need! But, I can't speak German, so I'm not real comfortable
about pursuing this route.
> I was wondering if anyone on this list had any extra of these that I could
purchase or knows of a supplier where I can just BUY what I need.