I own one. The promag 15 round magazine works with the 92S.

Yes magazines are readily available for this gun. Buds has them in stock and they also have extended round magazines as well.

Should take normal Beretta M9/92fs mags. Some magazines may requre some small amount of modification do to differences in the mag catch (you can do this with a dremel or some cheap files), but aside from that you have nothing to worry about. Old Beretta 92 mags will fit fine unmodified.