We made tops for a 125 gallon aquarium out of plexiglass. Cut it to to fit, drill some ventilation holes, and then use mirror mounting clips attached to the plastic top to hold the plexiglass in place.
Mirror mounting clip: http://www.lowes.com/pd_197434-405-5...ductId=1056915 - just don't screw them down tightly so you can rotate them out of the way when you want to lift off the top.
They retain humidity much better than the mesh lids.
How would I use a heat lamp in this instance or would an UTH be sufficient enough?