*Posting for anyone who has a similar question *
After some measurements, the cut into the reciever is a unique European style, and doesn't conform to anything easily available on the market. The dovetail measures 11.6mm at the narrowest, and ~14mm at widest. From base to apex, approx 3.8mm. Not exactly gunsmith tools, but you get the idea. There are companies out there that make bases which would fit, but require gunsmithing to grind into the right fit. Frankly not worth the cost. Unfortunately there's only 22mm of reciever unmolested to work with for a more conventional base. Typical weaver mounts look to need about that much between holes, leaving not enough mental. I could bridge that gap if I want to get creative. Leupold makes some 2pc M98 bases that clear the charger hump, and I could slide the base so that one hole is on one side of the gap, one on another.
Worst comes to worst, sidemount is a potential option