need ideas for a new lid

I have a pair of mali uromastyx, in an odd-size tank. The tank came with a sliding lid, but it was broken, so I replaced it with a lid I found on clearance at petco. This lid was basically a plastic frame with metal screen, and two holes in the top for lights to go in. The lid is adjustable in length, so it fits my odd-size tank just fine.
Problem is, I have a 150 watt heat lamp on the tank, and I have accidentally nudged the lamp while doing maintenance on my other critters. I have the tank on the bottom shelf of one of those metal storage shelves. When the lamp gets moved off center, it melts the plastic of the lid, creating horrible plastic smoke and fumes, that give me an awful headache, and can't be good for the critters.

I need to make a new lid for the tank- preferably something that will allow me easy access for feeding and maintenance. Its an odd-sized tank, so buying a new, metal screen lid isn't an option for me. A light stand won't work because there isn't much vertical space on that shelf, so the light has to be resting on top of the lid.

I tried leaving the lid off, as i was under the impression that uromastyx don't climb or jump. Then I found one of them outside the tank, trying desperately to get back in.

Any ideas on how I can make a new lid that won't melt/burn from the heat lamp?

One thing that you can do is take buy some 1x1's and cut them to size and buy some screen and build the top to that size and stape the screen to it. That would make the lid heavier and it would be a perfect fit.

I've made screen tops for odd size/shaped tanks using wood and screen before, so that is an option.

Depending on how the petco top is made, you might be able to rig some "keepers" for the light fixture. The first thing that comes to mind is to simply glue or screw some little blocks of wood around the light fixture to prevent the fixtures from sliding.

Steve