Water hides?

I'm trying to balance out my setup for my new baby ball. I'm a first time owner and want to do it right. I have a nice terrarium (that's wood and acrylic) and I'm using ceramic heat for at night. My problem is humidity. Its hard to keep up. I wanted to try to give the little guy a water hide or a damp hide. I haven't found anything on how to make them. What do you do? What are your ideas? Any help would be very appreciated. Thanks!

You could hot glue some spagnum moss inside the top of hide, mist it occasionally.

That could work but I have found that sphagnum moss brakes down pretty quick. I'll have to give it a try.