Not sure if you will get this over the pond, but here we have really useful boxes. There's a company that sells adhesive magnetic ferro sheet that are fit to size for these boxes.
http://www.tinytintroops.co.uk/Bases/Flex_Mag_sheets.htm I've been moving all my
40k stuff to this method for storage and transportation.
With enough Magents you can keep chunky metals in place
lol. Plastics are perfect for that.