I want to do one on the passenger footwell in which case you could have mine, but I might try and sell my car so not sure what I am going to do. I'll pm you.
i have a double 8" enclosure, vented, about .6 cubic foot for each. it sits on the trunk floor though, made of 1/2" mdf. very sturdy. $$ to ship from philly to you though...
I seriously doubt anyone would sell a pre-made sub enclosure for Vipers.