Atlantic Firearms has the (.223) PAP M90 NP now on their website: "in stock". These are manufactured with adapters designed to accept AR magazines: plastic, but reportedly very durable. Approx. $800 or so.
I bought a 'nib' Saiga .223 two weeks ago, and it will stay original. The trigger is pretty good, shorter pull than both of my SKS, and a bit crisp.
There might not be any gun smith in the Memphis area who has installed the bullet guide with which the Saiga .223 might accept AR mags---reliably.
The Izhmash 10rd. magazines are very hard to locate, but I found two of them.
2afreedom: have you tried a few different SGM 20-rd. mags in the Saiga .223?
A few skeptical reports I read about them seemed to be first-hand, but can't remember which of their mag capacities were mentioned. This basic gun really is a lot of fun, even with simple slow fire.