If you buy a set of Burris 30mm Signature rings they will come with replacement offset ring inserts with the rings. They are not figured in moa however but instead in +/-0.010"
You can put a -0.010" on the bottom of the front ring, a +0.010" on the top of the front ring and the opposite on the rear ring to get a total of +0.020" cant.
If you can not find the loose inserts, let me know, I may have some loose sets floating around the shop I would give you if you mailing cost which would not be much.
Let me know,
Kirby Allen(50)