I have some very tiny parts that get still fall out of the, Stanley 014725 25-Removable Compartment Professional Organizer when it is closed.

I designed this small lid to prevent very tiny parts from falling out. Note that the little nubs on the lid are a tight fit and help to press down on the lid. I also don't think you could put this lid on all of the small containers as there isn't enough clearance between them. However it seems to work on a couple of them, which is all I needed.

It also works on great divided containers: westendriot's excellent small divided bin