Send tantal an email and request his latest price list. You might tell him you are looking to find a PK-AS-S. That way if he is out of them he could tell you when or if he will be getting more in.
The email addy is email@example.com
Doug is good people. He's also located in Texas so the shipping prices are low and it won't take very long.
I'd hold out for the one with the AK style mount, the PK-AS-S.
The other one that uses and AK mount is the PK-AS-V (v for Vepr). It moves the optic over the centerline of the rifle. It will also block you view of the iron sights. I like the way the PK-AS-S is offset to the left. It puts the optic in front of your eyes without making you lean over. Perfect for the S-12 IMHO.