If you want to go with a solid top instead of the screen, you can mount a Radiant Heat Panel to the inside top. Here is a link....http://www.reptilebasics.com/rbi-radiant-heat-panels

They are a little pricey at first, but last damn near forever unlike heat lamps or ceramic heat emitters. I use these in my display cages and they are awesome. If you email Rich at Reptile Basics with your cage dimensions he will tell you exactly what size RHP you need. He is a great guy to deal with.