I got mine on Ebay.. I had to buy the bolts, lock washers and fender washers from Sears Hardware and a grille ($10) from a local stereo shop. Use undercoating on the installed bolts to protect from rust on the newly drilled holes. A bit harder to install without the drilling template, but take your time and measure twice, drill once! Be sure the trim fits in the same screw holes before drilling!
If you want new, check with local dealers.. I think there's a dealer locator on JL's site.
Otherwise, do a search on ebay for stealth box and stealthbox (no space) Otherwise thunderform (MTX version) or Qlogic and q logic and q-logic for the Qlogic version.. They show up from time to time..
Expect to pay $250 - $395 for used to new.. I did see a guy that was selling new for $310-$325 on ebay, but that was a while back..
Good luck.. I'm still waiting on my amp to fire the puppy up!
Take care,
JK