If I needed to boost humidity at all I could take a warm wet rag and place it in my bra as well but not on/touching the egg. I bet that would work.
That might work but I would be careful because it may also lower your temperature. I'm a spaz about keeping humidity just right and I wouldn't tell you not to worry if I thought it would be to the chicks detriment but I really think in this case there's no reason to worry about humidity in the boob-bator. Perfect humidity built in. lol