RCBS also makes them special order..... You will have to get an RCBS dealer to order them for you and be prepared to pay dearly.....
Quite a few of the special order RCBS dies are actually in stock at Huntington Die Specialties in California, they might have but yes, very expensive.
On the other hand, C-H dies are less expensive and equal for quality.
CH are pretty descent dies, may just have to go that route.
It's a ruger number 1 and will know when it arrives if it is a factory barrel or a rebarrel job but it should be a interesting hard hitter either way