Do you care about looks? Before, I have found 120g acrylic tanks and just cut them in half on a table saw. Cheap, but do not look the best and are right at home in my basement sump room.
You could also make your own or call custom aquariums... most places should be about to do 48x24x12 if you do not need that extra inch.
The low boys are nice, but FWICT you have to find the locally since nobody will ship them. They are only 10 inches high, though, and you have to drill them yourself.