Congrats! I have had my ZKM 611 for about 10-12 years. Great little rifle! I won't sell any mags, though. I have seen some around, so will keep my eyes open for you. They also had some 10rd mags. I don't have any of those, though.
Mine is accurate and reliable, but after about 100 rds needs to be cleaned. The action fills with unburned powder and it starts to choke.
My good friend got his at the same time I got mine. He chopped his bbl down to 16". Very cool. And he has 3 of the 10rd mags.
Be careful when disassembling. I chipped an ear off the tiny little "Jesus Clip" on the end of the recoil spring, by letting it "snap" while cleaning. It still works and I have not bothered to replace it, but it is broken.