This might be of interest, if you haven't already seen it.
http://applications.zeiss.com/C12578620052CA69/0/D64453B7717B7F54C12578690032ABA6/$file/planar1-2_85mm_e.pdf
As for the source of filters and lens shades, then you can either use round or square filters. The choices for round will be Contax themselves, Schneider/B+W, Heliopan or Leica, as they all make top class glass in substantial brass mounts. There are many available second-hand. The same goes for the metal and rubber lens shades.
For the square filter systems, then there are Lee, Formatt, Cokin, etc. The advantage here is that you buy suitable mount adaptors for the lenses and just one set of filters. The systems are much more expensive, but in the end are more flexible. I can use my Lee filters and bellows shade with my Contax SLRs, Leica Ms and 5X4 camera (all on a tripod, as using the big bellows on a Leica M handheld can be troublesome as you can't see a thing through the rangefinder!).
Nick