Normally when you buy stereo equipment, or computer parts from overseas, you often find packets of 'Silica Gel' in them. Instead of throwing them out, I save them and use them for stuff like this. I keep my welding rods dry with them, keep one in our safety deposit box with our important papers, and various places like that. You can reactivate it by putting it in the oven at low temperature for a little while... You can buy it at hobby shops also; it is used by hobbyists to dry apples for making little dried apple dolls.
Anyway, you might consider using that.
In the marine industry where boat-owners are used to having a huge amount of condensation, they hang these things called "Dri-Z-Air" in their boats. It's a little plastic bucket suspended from a small hemispherical mesh container into which you pour calcium chloride powder (I think that's what it is)... The powder absorbs the moisture from the air and deposits liquid into the bucket below. About once every week, you visit your boat, empty the liquid, restock the calcium chloride, and it keeps the mold at bay.
Here's a link to it: http://www.drytheair.com/
You can buy their crystals to replenish the container but my dad used to buy 20kg bags of it for the same price as their little bag. You don't even need to buy their little container. You can just suspend a kitchen strainer over a little ice-cream bucket and accomplish the same thing.