I get my leather bits from Bedford Tack in Bell Buckle, TN. They keep them stocked now but custom make them within the day for misc sizes. Order 1/4-1/2" bigger than normal. They're loose rings but they're not really loose. They may be able to do it as a D if they cut down a regular bit- would be more $, of course, but the loose ring is less than $20 so not a lot. They bevel the leather so it's round. My girls really like them!!
Sounds like the Beris isn't quite ready yet but they will be in at some point this year.
For now I just ordered a Nathe loose ring from VTO.
Will get on board with a Beris D or Fullcheek when they are in stock her in the USA.
They do have some in stock now but not what I need.
here is the link to the CO company that carries Beris.