Two weeks !!!???
Two pieces of scrap plexi 1/4 is great to work; I just came back from the Hospital, had to take a class there so I'll check the local TAP later. The box can be taller than the aquarium since it can be shortened at the base. aquatraders has a triangular overflow box, can't remember the price but I don't think that pricey. I find egg-crate better myself since it allows for nice flow, the routed teeth if they get clogged, flow decreases significantly.
You will need a bulkhead and PVC pipe, a PVC Tee, Cap and a 90 elbow for the Durso style OF drain pipe.