You can usually find a bulk supplier of AK rounds and stripper clips. I still have a case I bought six+ years ago (I don't plink with the SKS as much as I used to).
Also, there are both mag conversions (which I suppose are more complicated), and deeper magazine wells (from 10 to 20 to 30 round capacity) that can be fitted to SKS's out there. Mine has a 30 round well, and I load it with rounds from stripper clips.
As I've had this one for 15+ years, I don't have any recent info for you. Russian 7.62mm rounds nearly as cheap to buy in bulk as .22 short.... and a whole lot more fun.