I made a simple two piece glass top for my 55 gallon a while ago out of Jalousie window. I don't remember the shop, but basically any glass shop, ask for Jalousie in the widths you want, most common are 4 and 6 inch widths and usually, they cut to length for free. You want the clear type, non frosted or textured. I found these are great and cheaper than store bought, the edges are finished already, so only the ends are rough. only thing is you have to make your own handles if you want, I didn't bother since it was two piece, just slide them around and grab the whole glass.