If you're going to Allentown in the spring, there will likely be tons of old ones for cheap. There was this year, anyways. One guy had a stack of them leaning against the wall. (It reminded me of flipping through records in a milk crate) All I bought was this Gottlieb Dragon PF, for like, $10 I think.
I wish I had grabbed more. My original idea was to practice playfield touch-ups on it, but never got around to it. If there's more like that next year I'll likely buy a stack of 'em.
I bought a Twin Win PF from Mike Hanley in Ottawa this year. It's pretty much in the same shape as the Dragon PF, only it has many of the inserts in it.
If I ever hear of anyone who is looking for these (or any PF's I get in the future) for a project/resto, I'll be happy to pass them along.