I found the enclosure on Ebay, missed the end of the auction (it didnt meet reserve), then found the guy on craigslist and got the enclosure for $275 shipped.

He custom makes these, although I'm sure a custom one would be more than $275. This one was apparently out of his own vehicle and originally had a JL Audio W7 mounted; I had to dremel out the speaker mount by about 1/3 inch so my W3 would fit.