Enclosure lid

Hey there again, I already posted today but I have more questions.

What is the best way to make a lid for this tank? I lost the original lid and I think it would be better for everyone if my T was secured.
Any ideas?

I usually cut a piece of plexi or lexan to fit. It's easy to cut, can be drilled or cut out for ventilation and it's clear so you can see what you're about to unleash before the lid comes off. You can get it at most any home improvement store