Are this available in multiple fitments like the resin conces? (i only see 2 size options). Ideally I need a 1/2 - 20 RHT on this medium diamond cone

The more generic abrasive cones are only availble in 5/8-11 and 1-14 threading. The custom cones from Abrasive Tech can be made with any shaft and threading. They also have specific grit levels available. They are more expensive and have a 4-5 week lead time since they are custom made.