You can try local salvage yards looking for well-used original parts. You also can go to swap meets, or search the Web, where you're likely to pay top dollar.
And of course there are those independent catalogs that feature parts manufactured who-knows-where.
But now, if you have an old muscle car or other classic, you might be able to get parts from the dealer.
General Motors has 150 suppliers producing restoration parts that are sold through dealers. Ford and Chrysler also offer some classic parts through their catalogs.
You see, it's not so bad getting old.