Some of the professional motion picture houses in Hollywood might be a good bet. Birns & Sawyer, etc. Sent a few Nikon lenses to Mel Pierce for very well done repairs and modifications...back in the 80's.
Would recommend running it up the flagpole on this forum...http://www.kyphoto.com/cgi-bin/forum/discus.cgi
They helped me out with the same problem on an old 28mm AIS. Sloppy focus rings can seriously degrade optical performance. Unfortunately, all the advice I got there and also from the local repair houses was basically "find a tighter sample and save yourself some money." Replacing worn focusing threads is pretty expensive, usually requiring at least a sacrificial other lens with perhaps damaged optics.
And FWIW, have found that on digital cameras the 35 f2 is kinda disappointing, lotsa chromatic and edge aberration that didn't used to show up on film. The 35 f2.8 works a lot nicer for me.