Thanks for asking. We love helping people research and find the bikes and equipment they're looking for. It's what BikeRoar is all about!
What he'll likely need is 16" wheel bike. Be sure to visit a local bike shop for one - don't buy it from a mass market / big box retailer. A local shop will help you identify the right bike and you'll almost certainly get one that's better quality.
Please try our local bike shop finder. http://www.bikeroar.com/stores.