You can put foil, plastic or even a damp towel over parts of the screen top. You could change to a substrate that holds moisture better. You could add sphagnum moss. Increase the size of the water dish. Also Che’s are horrible for humidity, I heat my tanks with infrared bulbs on a dimmer. Che’s get two if not three times as hot at the base then a comparable bulb. I also use a very large humidifier. I sure many more will chime in with much more advise. But that’s some ideas and starting advice. Hope it helps!
All good tips...If you've got room to add a 2nd water bowl that helps too. I put 2 in all my enclosures except my little hognose since he doesn't require higher humidity.