I've tried the Tropic-Aire and it works great. Just be sure to buy an air pump rated for a larger tank than what you have.

But with glass tanks and screen lids, by far the easiest solution is to cover with damp towels and/or duct tape (outside top of screen lid). Also I've heard using Bed-a-Beast substrate does wonders for humidity - plus you can feed on it and it looks natural.