Just go to lowes and get 1/8 inch glass cut there....it will be thin but since its gonna be for a small tank there shouldnt be a fish big enough to crack it ......just silicon some kind of knob to make the front piece easy to remove........i did this for a 20 long before ....cost less then $10.....i even did this for a 40 breeder....it bowed a slight bit on the 40 but worked well for the 20L