Hi Pepe. Thanks for posting here. My solution for a 34mm diameter sight was to use Blaser R93 34mm rings (made from aluminium), mounted on a Mauser M03 Double Square Mount bridge. Here's a link with some pics of how that turned out. It's worked a treat.

I'm thinking you'll be able to find these rings at any dealer that sells Blaser and Mauser rifles. I bought mine through Miall's Gun Shop in Frankston, Victoria, Australia. I hope this helps. Let us know how you get on.
Regards, Rick.