Has everybody noticed the excellent new ranges of upmarket (Tupmarket ?) type re-sealable plastic containers now on the market ? Two main brands that I've seen -
Lock & Lock
Really Useful - sold by Staples and Rymans amongst others
There are other cheaper lookalikes too. More rigid than Tupperware, all in a very wide range of shapes and sizes (and colours), and good for almost anything you want to keep clean and dry onsite, from QM and igniters to larger items. I use one of the medium size Really Useful boxes to house a Chinese 20-channel wireless system. It's big enough to carry the system and its accessories, and with a few strategically drilled holes for igniter wires and aerial, it makes a good weatherproof (tho not pyro proof !) field case.