Ok so I was thinking about this rust thing more, and in my last response I talked about preventing rust caused by using Madacide, but it doesn't even seem like that was the problem in the original post, it was just caused by high humidity.
SO, I came up with a really simple solution, which is to store machines in an airtight container like a tupperware container or something like that, and include a desiccant packet. You know the little packets of humidity absorbing crystals that come in shoes always labeled "do not eat." The more I think about it the more I like the idea for traveling or for people who live in places like Florida or the tropics. Not only does it keep your machines nice and dry to keep them from rusting, but a dry environment is less hospitable for bacteria, which is a nice added bonus. Win win!