Custom Box problem

I have a 2001 Frontier crew cab. I cant find a box to fit behind the rear seat. so if anyone knows of a box or a place that would tell me how to make it, that would be awesome. I would like to put three 8" subs behind the seat, but I will take what I can get.

Thanks
Cody

where in wisconsin do you live? based on that i could find a place or my uncle who lives in greenbay could:licker:

I live in Hortonville, only a few mintues out side of appleton