This post ASS-U-MEs that standard AR-15 .22LR magazines will fit. I am not sure about this. Check this first -- and if they don't, buy something else. There are now many, many vendors with a diverse array of .22LR AR options out there, so make sure you're getting exactly what you want. Somebody will sell it to you.
Now, on to the magazines...
I have a 10-round Ciener magazine, which is by far the easiest and most pleasant .22 stack magazine I've ever loaded. The spring tension is just right, and you never have to fight it. They don't look like regular magazines, but they work exceedingly well.
http://www.22lrconversions.com/atch-pg.htm
Black dog makes 10, 15 and 26 round full-body mags. I have the hi-cap version. It is not as pleasant to load, and it's plastic, including the feed lips, where the Ciener is parkerized steel throughout. However, the Black Dog magazines handle like the real thing, and this is good for practice, and mine works fine.
http://blackdogmachinellc.net/ciener-full-body-mags.aspx
You pays your money, and you makes your choice.