OK, here I go with my own little mantra (with apologies to Eric) - "Salvage yards, Salvage yards, sis-boom-bah".
When it comes to these sort of items, I always check there first. These types of things are rarely still available and if they are, they are priced as George indicated.

OK, they won't be brand new and may require some "touch up" work, but I usually find what I'm after for somewhere in the $50 range. You may have to scrounge a bit, but they are out there.
There are lot's of salvage yards, but my top two are:
Specialty Aircraft - Redmond, OR
http://www.specialtyaircraft.com
800-500-6786 - great folks. They'll take digital photos of their stuff and email it to you so you can "shop online".
Wentworth Aircraft - Minneapolis, MN -
http://www.wentworthaircraft.com
800-4WENTWORTH
Check TAP - there are a bunch more good ones. I'm slowly aquiring panel parts to restore my '52 panel. You know those bezels that go around the instruments? Last time I checked with Univair they were $122 EACH

- I picked up a half dozen from Specialty Aircraft two years ago for $8 each. Quite a difference.