Here’s a 30 round mag for the Saiga 12.
http://www.youtube.com/watch?v=F1vPXTcE5-4
Yes, but reliability on those is spotty per reports. But yes, drums do seem to be the way to go on those - though MD Arms (the guy who made the first reliable 20 rd drum for the S12 that didn’t require you to hack up the gun) is now working on a reliable double stack stick mag for the weapon.