29'er wheels are the same ERD as 700c road wheels, so '700c' road or hybrid tires would work.
ALEX list the rim as a 19mm width, so you could concievably go as small as a 28mm road tire.

I'd stick with something in the 35mm-38mm range, which should give you a faster tire, but still have enough volume to absorb bumps, debris, and the occasional curb-hop.

You may want to stay with a larger tire,but just a smooth tread like a Schwalbe Big Apple 2.1" I find that urban riding is a lot like fast trail work, and the big volume helps shake off obstacles and road hazards.