Decware offers DIY subwoofer cabinet plans/kits. You may want to contact them to see if any of these work for you. If you find something that works, Meniscus Audio is one (I'm pretty sure there are others out there) company that will supply drivers/materials and build from your plans. Never heard these products, so I can't speak to the results - just FYI.
Good Luck
Marty
Good Luck
Marty