Someone suggested Brownells' gel packs, which is a
thought, but I was
specifically interested in the little white bags/plastic canisters that
I can just toss in a box.
But I must wonder if this will serve our purposes. One little
pack only absorbs only a small amount of water - then it stops.
I was thinking a larger quantity, though ^_^
I think these things are meant for closed boxes
going from
factory to shipping container to warehouse to store, and
shouldn't be expected to reduce humidity by significant
amounts over long durations.
This does make me lean more towards the Brownells' devices, which are
"rechargeable" (but somewhat expensive given the number of equipment boxes
I've got).
They aren't replacements for dehumidifiers, you'll
be disappointed. They are only meant for use in closed,
relatively-low-humidity environments, like sealed packing boxes
that were packed in a decent environment in the first place.
If exposed to the atmosphere, where moisture is essentially
limitless, they'll go inert shortly.