You can make your own lid with a sheet of polycarbonate cut to size. Just drill some holes about every 3/4ths an inch for gas exchange and place a couple aquarium lip clips. For a ReefCasa tank it probably wouldn't cost more than $25.00usd to make your own lid.
Basically, something like this, only instead of using glass you use polycarbonate (not acrylic because it will warp) and drill a pattern of holes to make it look nice and for gas exchange.
Basically, something like this, only instead of using glass you use polycarbonate (not acrylic because it will warp) and drill a pattern of holes to make it look nice and for gas exchange.