I would recommend you get Blitzu or Knog - especially for a child. They are bright, waterproof and attach anywhere. They are sold on eBay and in sporting goods stores - they are inexpensive and really add safety.

I tried a bunch of budget models until I found the safety light on this page. It's a completely different level. The light is very powerful. And this is despite the fact that the device is compact, lightweight and can be attached to almost anything. The device has a durable case, protection from water, dust and impacts, the ability to turn on red, white or blue light. Ideal for both adults and children. Plus, the price is just great.