I called K&G before posting this, and was told they are out of steel disks and now have an Al one. Paraphrasing and reading between the lines, it sounds like they are having trouble finding a supplier to make more steel ones and/or it's too expensive to make more. Texas Knife Supply told me they are 'looking for a supplier to make them' and it probably wouldn't happen anytime soon.
What is wrong with it JB? Maybe I will buy it from you
That looks interesting, but I think that's for the disk only and looks like some other parts would be needed. Also, is it for a keyed 5/8" motor shaft?