We always have a good selection of these, ranging from cheap moels that might put one trainee thru basic, to bikes built to aduld standards, for families considering a sequence of small riders. Almost n the former class is a sort of cgild's seat with wheels, pedals and a handle. It looks like a garden tool, but it may be an efficient way to learn about balance and pedals. unfortunately, no photo available.
Apart from the well-known bikes like Trek or Electra. kid's bikes, there are a lot of smallbikes posing as BMX bikes, and some smaller full-on BMX bikes suitable for younger riders,though you probably dont want a h/d adult-capable bike for this. The nice thing about bikes in this group is that they have the stamina to become hand-me-downs, with a story of their own.