Congrats on the pistol, they are a ton of fun to shoot.
I cannot yet comment on the sights. I have a brand-new set of 10-8s for my M&P22 just sitting there but cannot find the time to install them. Maybe this weekend.
About the magazines, try 44mag.com. I also recommend a mag loader from Brass stacker and maybe about 1000 or so rounds of CCI Mini Mag Solids...
Congrats on the 22. It is a really fun shooter. The sights are sized the same as the FS 9 but the slide is alum. so be careful when installing the steel sights on the alum. slide.