How about keeping a bottle of water in the fridge and then misting the enclosure once or twice a day? I wonder how effective that would work. Or maybe take a reusable ice pack, and bury it under the substrate, just need to find one thats not to big so that it doesnt freeze the newts, and one thats not to small so that it doesnt thaw out to soon. Ive read something about putting a small tank inside a larger tank and giving it a 'water bath'. Just keep the larger tank filled with cooler water and icecube/packs and that will draw heat out of the smaller tank. Im glad I moved out of an apartment and got my first house with a basement, I was using 8 icepacks everyday. Had no room in the freezer for anything else! Hope you find a solution!