I have a Brno #4 with the 16mm dovetail and used a set of CZ rings that came with one of my 527 rifles. The ring intended for the rear has a recoil lug that needed to be removed, but a little dremel and file work and then some cold blue took care of this.
I think any rings for a 527 should work, with the recoil lug removed. Leupold,and Burris make rings for the 527, in addition to Warne and CZ. Talley might also, but theirs I am familiar with are a vertical split which you stated was not your preference.
If you are interested in a set of the cz rings, let me know. I may have another extra set that is new that I would sell.