In my experience _everything_ that has been recorded
since about
1917 is available on cd if you go to the right sources.
There are boutique operations that, for a medium-sized pile of legal
tender, offer rare recordings on CD-R, but I've never used them--
their prices are more than I can stomach.
On a related note, and definitely vintage, there's a radio (both FM
and internet) program that digs around through the Thomas Edison
collection of discs and cylinders that's quite interesting:
http://www.wfmu.org/playlists/TE
Cheers,
Chuck