I had a similar issue with humidity, as it gets desert-dry in my section of the world in the winter. I've been able to hold it steady at 50% for the last few weeks by covering just under half of the screen with a damp dish rag with a large book over it (the book is more for cage security, lol). Probably 2/3 or even 3/4 of the screen top is completely covered by the rag/book setup, heat lamp & a smaller book to help secure the other side of the cage. A daily spritzing on his fake plants & re-wetting the towel once per day is all the extra work I've needed to do. & Anicho hates the spritzer with a passion. I try to focus the spritzing on whichever side of the tank he's not on, with limited success.