Dang, checked all my usual sources, all out. Not much brass out there either! There is some on Gunbroker. You can put a backorder in at Starline.
Suggest you keep checking ebay, and put in an alert at Buffalo Arms. Your RB should like .515s, so any die set will work. IF I understand the swapping around going on above us, seems one of those guys should have an extra set you can borrow?