NB Molded Fiberglass Sub enclosure
 

Molded Fiberglass Subwoofer Enclosures: $200 shipped. If there is want for a modification of the design, just ask. I would be willing for the right price or if a few other people were interested in the same. Subwoofer in the picture is a 10", and the box is made to (just barely) bolt on a 12 if thats what you want to use.

Update, picture of completed enclosure.

Would look even nicer if you built an enclosure for the other side. Good work.

Is it completely sealed or is it open on the back?

It is a sealed enclosure