Trying To Find/make A Lid For A Large Hex Tank

I'm not sure about the exact gallons, but I bought a pretty large hex tank for $50 today (I couldn't say no. It was clean, included the matching stand, and almost walking distance from my house). The measurements are

height: 29 in
width across: 27-ish in
pane size of the six sides: 16in x 29in
(if my roommate's math is right, its around 80 gallons or so?).

The only real drawback is that the seller has no lid for it. I don't mind an open aquarium, but my precious and fat little cat can't swim to save her life and, in all of her infinite wisdom, sits on or tries to play in all of my fishtanks (I've tried just about everything to stop her except maybe tying her to the coffee table or something). I don't have a specific room for my fishtanks, but I will be putting this one in my room where she isn't allowed, which should stop most of her shenanigans. All the same, I don't want to chance coming home from class and finding her stuck in my tank and struggling to get out, or worse. I just want to minimize injury/death to the cat and the fish.

I was thinking maybe a mesh or some kind of acrylic top? I'd love suggestions for what you think, alternatives, etc.. As long as it can hold 10-15 lbs in short bursts. I realize that the width of the tank might make that difficult structurally, so I was thinking about putting in a bar on top in the middle as a support and maybe a place to attach hinges so I don't have to completely remove the lid all the time/to make it less prone to breaking.

I would also like some suggestions for lighting for the aquarium. I live plant all of my tanks, so I would hate to waste this aquascaping opportunity, especially since this will be my largest tank.

 

A cable spool would look kinda cool, stick a spot halogen down through the middle and laugh at everyone's face when they see it

 

You could buy and cut out a piece of plexiglass/acrylic. That's what all my tanks lids are made of. It can kind of be expensive though.

 

A cable spool would look kinda cool, stick a spot halogen down through the middle and laugh at everyone's face when they see it

I'm new to the DIY scene (since I just now have my own place and can buy my own aquariums without being judged for all of my "fish buckets," as my grandmother called them) so can you please explain what this is and how to do it or where to find a tutorial? I'm assuming you put a clear pipe in the middle, seal it, and run lights inside it? I want it to be as bright as possible for the plants, of course, and I would love if I could also do a blue nighttime light too.

You could buy and cut out a piece of plexiglass/acrylic. That's what all my tanks lids are made of. It can kind of be expensive though.

Also, upon picking up the aquarium from the previous owner I realized that the top has no lip on the trim. The PO didn't use a light for the tank, but my room is dark and if I'm sinking a few hundred dollars of my broke-college-kid amount of money into it, I would like to actually see my fish and let them live lol do you think that the plexiglass/acrylic would stay on well? My roommate's dad is over the entire wood section of our local Home Depot (doors and windows included) and could probably get me a nice piece or two of either for relatively cheap from the cuttings/castoffs/broken pieces. If I do a hinge in the middle, it'll need to be smaller than the whole piece anyways.

I could also do a wooden cabinet and hood for it. My roommate mentioned maybe making the hood of wood and painting the inside with a sealant to keep it from rotting away. Thoughts? Again, her dad can help us get the wood cheaper as pieces of appropriate size become available.

 

No modification would be required for a cable spool, except for maybe a feeding hole and a small slot for filter/cords/tubing.
A heat lamp housing from a farm supply store would work too, if you like the industrial look. Some small holes would have to be drilled near the top to allow airflow, but an A19 LED bulb would minimize heat.
There's lots of things you could do, including making a lip and using acrylic. It all depends on what you're looking for.