Thanks everyone for their suggestions! The link for Commodity Axis T5 might be worth a try, but I really do not want to have to build a canopy. I really like the look of an open top aquarium.
BlueRam are suggesting OD the regular T5's in the fixture? I'd really be interested if you would point in the right direction.
Bombay, thanks for the links but a 20L is 30" long. None of the fixture on that site are fit for my tank.