I may have what you are looking for. I have an acrylic sump that is basically a rectangle that has a divider that starts at the top but does not go all the way to the bottom. It stops about 2-3" from the bottom. I believe it may have been for a sponge filter but you don't have to have one to use it as a sump. I don't know the exact measurements, but I know is is very, very close to what you want. It also has a bulkhead already installed at each end. If you are interested I will measure it for you. I live around Chicago.
Ray
