Go to any window or glass shop. You should be able to custom order any size you want in either acrylic or glass. Also, the bigger the city the more choices and more competetive rates.
I am from Belleville. There are a few places near by. I work for a place that makes HUGE marine windows (big aquarium glass) and I want to shop around before I check out how I can get some glass.
I bought super clear (I think that is the brand name) tempered 1/2" glass. I ended up paying 711.00 USD for two pices of 94.25x25.825x.5. This was the best price I could find after getting quotes at 12 differen glass suppliers.
go find a custom fish tank store and buy the glass there. they usually just charge a buttload of money for building the tank even though the glass is relatively cheap. I spent months trying to find a good place to get glass. kept coming up with quote like 400 dollars for one piece of glass because the thickness I needed was not standard stock. finally found a custom shop and i got the piece for only 80 bucks!