I'm a bit confused as you have F2 in the title and S2 in the post. If you want an F2 lens (SLR) there's plenty of Non-AI nikkor glass on ebay - 50mm F2, 105mm F2.5 are both great lenses, the 35mm f2.8 is apparently a bit of a 'dog' and should be avoided...
If you're talking about an S2 (Rangefinder) there isn't much glass for it outside of that era - EXCEPT that there are some modern voigtlander optics (referred to as S-mount). A 50mm 1.8/1.4 would probably work well on it.
Hope that helps!
~S