Had the same problem. Things you can do to boost humidity in tanks
-Cover 90% of the top with aluminium foil
-Cover 90% of the top with cling wrap
-Combination of covering the top with aluminium foil then cling wrap on top of that. Seals in heat and humidity. Make sure to not cover 100% though, enclosure still needs ventilation.
-Put damp sphagnum moss in the enclosure in combination with covering the top. The moss holds a lot of moisture so it helps.
-Change your substrate/bedding to "Eco Earth" which is just coconut, or "Cypress Mulch", both boost humidity very good. You can even use a combination of the two, blended for even better effect.
If all that still doesn't work then invest in plexi glass top yes. And if that still! doesn't work then try a fogger for the enclosure that's on a timer, wont have to worry about misting ever again.