i always through those luittle silica gel packets in with my ammo.
go dumspter diving behoind the hospitals and find the cases they get ultrasound transducers in. ive got 7 of those, and as i understand it they just throw them away when they are done with them (i got mine from a relative who used to be an ultrasound tech) . they make for good pistol / optics cases too if you leave the eggshell padding in them. plus they are beta gamma and EM radiation sheilded.
(atleast i think thats what those symbols on the cases mean)