I can't help you at all relative to your question of continued use of the panel.
However, here's a start to search for breakers. Some of these are listed as "used" breakers. (I wonder if there are problems with liability from installing used equipment?)
http://www.electricsupplyonline.com/circuit_breakers-murray.php http://www.allbreakers.com/store.asp/pg!products/grp!325
http://www.globeelec.com/Specialties/specialties.html
