I would vote a second option for bar end or downtube shifters (or some kind of bar mounted option, I know there are a few). It would let you regain your shifting without prohibitive cost. Given the commute you describe, I bet you do not shift a whole lot during your trip, so you probably won't see a huge loss of function by getting an "obsolete" shift system. I run bar ends for their cost and easy maintenance, and I think they are the nicest non-integrated shifter I have used.

If there are more problems than a broken shifter, or you are just looking for an excuse to buy a new bike, I would say look at some sort of internal geared hub. There are quite a few commuter bikes with them now; they offer low maintenance, simple solutions. Your commute certainly won't require more gearing than they provide and it gives you a nice sleek look. A single speed is also an option: it depends on how in love with gears you are.