I seem to remember a tan one recently, but don't remember whose it was.
Here is a sweet 12 for the backseat
http://www.tundrasolutions.com/forum...nally+finished
but may not be what you were looking for.
This solution
http://www.tundrasolutions.com/forum...om+stealth+box
is nice, but I think too small for a 12.
I don't know of anyone who is selling any customs. You could call up elemental designs and see if they have anything in the works. You may also want to try a local audio place and see if they are willing to build a custom box for you. You could also PM Texas Toys and see if you could pay him to make a similar version which could hold a 12.
Sorry man no easy solution, which is why a lot of people end up with the JL.