How can I find a filler panel to replace a car radio?

We pulled a 2-high radio with poor sound quality out of the dashboard of my son’s 2005 VW Golf. We replaced it with a standard height after-market radio with superior sound and features. But that leaves a gaping hole in the dashboard about the size of a standard car radio. I searched the Internet and JC Whitney catalog. Thought this would be easy, but found nothing.

Has anyone had to deal with this before? Am I just calling it the wrong thing, or do I have to break out the Plexiglas®, Bondo™ and paint and make the thing myself?