I just bought a beautiful Leica IIIF RD w/ ST and a like dew Leica M2 button. I already have a 50mm F1.5 Summarit and would like to find a 35mm to use on both. Plus I need a body cap for the screw mount and a rear cap for the Summarit. May want more accessories, but that is a start.
Many will malign the 35/3.5 Elmar since its been "improved" a couple of times but I think it's phenomenal. And it's very compact. I got an uncoated version from Youxin Ye and could not be happier with its performance. It's like nobody told this lens it's not supposed to be very good:
I'd never malign the Elmar 3.5cm F3.5! Another beauty from that era is the Hektor 2.8cm F6.3. These were cutting edge at the time, and they are still better built and smaller than most modern rangefinder lenses -wonderful examples of the Leica craft. With care they produce very good images by any standard.