I also struggled with trying to find the one piece glass cover for my 40 gallon breeder with no center brace. Sifted through the internet for days and finally tripped over it at Petco(actual store) a couple days ago for $35.
Made by Tetra.
Here is a screenshot of both the lid itself as well as the info on the box.
Good luck!
http://i.imgur.com/YpUuZep.jpg
http://i.imgur.com/CX6Q2N7.jpg