Ceramic balls may work,I have used them in my terrariums. I think you could keep up a high humidity with a cup half filled w.\ ceramic balls, a quarter filled w.\ H20, with pin holes. You find clay balls at spec. gardening stores. I have had success w.\ coco and long strand spag. moss. Also I would be scared for eggs sefety if left in cage, unless protected by a screen or something. Good Luck.