For my 22 gallon I ordered a custom cut piece of tempered glass from https://www.onedayglass.com/

I was even able to order a hole cut into it that I use as a grip when tanking it off and a spot to drop food in.

I had the glass cut about 2 inches less than I needed on the back and ordered this plastic strip that I stuck to the back and cut out holes for my HOB and a few other things: https://www.amazon.com/gp/aw/d/B000255O68

Then I used some vinyl H bracket things from Home Depot or Lowes to put around the edge of the glass piece so it would sit on top of the tank.

https://imgur.com/gallery/lusVszp

The only down side is the vinyl strips are white. I am going to order some clear ones online to replace them eventually.

Edit: the top isn't very noticeable when not looking down on the tank. It is on in the second picture on this post if you want to see it head on: https://www.reddit.com/r/PlantedTank/comments/bys9ce/2_months_progress_no_co2/