blind hem stitch foot for Necchi

I also read somewhere that it depends on the type of foot, and there are two general types of feet depending on how they attach to your machine?? I cannot find the article I read this on again, but I was wondering if anyone had an easy way to tell which type of feet to purchase?

You can purchase that presser foot here:

http://sewingpartsonline.com/blindstitch-foot-necchi-low-shank.aspx

Just make sure that you have a low shank. We've got a chart on telling which you have here:
http://sewingpartsonline.com/sewing-machine-pressure-feet.aspx