[Water Warrior 2]

Nice job and not an expensive storage box either. Those things are almost indestructable under anything except a nuclear blast. Just had a thought about the handle rattle. Get some velcro with tape on the back side. One piece on the lid and one piece under the handle. That should hold the handle under most conditions and the handle is still useable when needed.
A Dollar store, sewing center or Wally Word fabric dept should have the velcro.