Totally forgot about that whoops!
The best option in my opinion would be to buy a piece of plexi glass and cut it so there is a 2-4 inch gap on the side (for airflow) and a hole for the heat lamp.
You can buy sheets of plexi at the home depot as well as an acrylic cutter which makes cutting it very easy.
Ideally you don't want to use the heat lamp but if your room gets too cold then you might need it. The lamp is what will lower your humidity the most. Are you using a UTH or any other kind of heating other than the lamp?