You don't say what your budget is, but some of the Terry bikes might be small enough. The smallest sizes are made with 650C wheels, or with a 24" front wheel. That could make it a little trickier to find spare inner tubes, but it would most likely fit.
http://www.terrybicycles.com/Bicycle...o-Ride-Fitness
Extremely small adults also have a few junior choices available, such as the Kona Jake 24 (cyclocross), or some of the 24" wheel road bikes made by companies such as Pinerello and Argon 18. The components aren't top of the line, but those could be upgraded if they wore out.