You're referring to these...
http://www.sako.fi/optilockproducts.php?ringmounts
These are "Optilock" with the bushings, same as Burris Signature.
I looked high and low a couple years back for a set of these for a Tikka T3, couldn't find anywhere in N. America. Did find a listing for 'em in New Zealand, pretty pricey! I'd guess expect to pay in $150 + range. I wanted them specifically because I think a ring mount, because of fewer pieces and screws, is that much stronger and problem free.
I looked over Near Manufacturing's website, couldn't seem to find 'em there...???
But they sure do make some good looking rings! Serious stuff!