For sure! Some nice moistened sphagnum moss works great in a "humid-hide"- if you don't want to use a moisture-enhancing substrate throughout.
And restricting the air-flow: cover most of the screen, NOT with a moist towel (as heat is rising up & OUT of the tank, so that moisture is mostly NOT going into the tank where you need it) but cover most of the top with foil or plastic, thru which air does NOT flow -that will keep humidity inside where it's needed. If using UTH, put the water bowl over it part-way too