I can't believe that was the actual part number, I figured I was close but not on. I guess because it differs from there other part numbers and I've looked for it before.
As for getting the product, their site confuses me because they have plenty of links to buy product from them but no real ordering. You should be able to go to any installation place, the part is pretty common where even the smallest shop should carry it. If that doesn't work you can always go to Best Buy I know they have it. The part number may differ slightly but only by "BBY-" prefix to show it the retailer's. I'm sure you can try (dare I say it) Wal-Mart but I would try another auto parts store that's also likely to sell audio equipment like Pep Boys, Advance Auto or Auto Zone, then there is AutoBarn.
You can also order online at many stores including Crutchfield.
If you are really set on a compartment you can always get the trim off of another car and trim the piece so it will hot glue to the pocket or empty space