guitar amp thread
http://www.eurotubes.com/euro-j.htm
the tube store (canada )
http://thetubestore.com/el346ca7types.html
tube subing website
http://www.pacair.com/discus/messages/23/23.html
vaccumm tube world ??
http://www.vacuumtubes.com/6ca7.html
I'm not endorsing any of the above for purchassing or sourcing tubes from as I've no personal experience with most of them. I figured these links would help inform so some more intelligent choice could be made thereafter.
Only thing I'd also look into is the plate boltage or bias the maker of the amp intended for the tubes... although some are 'drop in exchanges, I'd prefer to know if I'm going to go another way... often minor voltage variances can and are acceptable.
I also agree with the mini remarks on the CED winged C the tube store posts.
if you need EL84... HAPPY GOOGLING!