I would go for a 35mm Summaron, or a budget Summicron like the one DF mentioned-2nd version??

Personally I would steer you far away from 3rd party lenses for your new M. Not to say many of them aren't superb, but that can be a long road that usually leads you back to Leica glass which can often be had for what is ultimately not that much more money, and a whole lot less hassle. Find a good user Summaron and you'll sleep better at night.