I bought it from pets-at-home of all places. They are sold as cold water tanks. It came with a filter but this wasn't very good. The tank and the glass are lovely though. It's 5mm ultra glass (whatever that is!) and has a lid and a sponge base too.
Best bit is that it was only £24! I went back and bought another one after I saw it set up.
I would phone ahead if you have any stores in your area, I think its proper name is just 25litre cube aquarium.