http://ball-pythons.net/forums/showt...=1#post1631478
I was having some humidity issues like you were. I've also been having a tough time keeping my tank as warm as I should. There is a video in the link that I shared (you may have to scroll down). It shows what one guy did to his tank screen. It's not the prettiest fanciest fix, but I bet that you have everything in your house right now to do it.
I did do mine a little differently though. I cut 2 holes for my lights. I did not have a piece of plexi glass for the sliding section, but I did put foil on another piece of card board instead. The new lid along with the wet wash cloth worked great. I actually had to turn of one of the lights because it was getting too warm and my humidity went right up to 58%!!!
At some point in time I think I will be buying/building something better, but for now, I'm happy. My tank doesn't have to be pretty. Everyone I know is too scared to come look at her anyway... lol. I just don't understand being afraid of snakes.