I usually find the parts I need from one or more of four places:
Digi-Key (
http://www.digikey.com)
Mouser (
http://www.mouser.com)
Down East Microwave (
http://www.downeastmicrowave.com)
RF Parts (
http://www.rfparts.com)
All of them have given me excellent service.
RF Parts has a lot of transmitting tubes, transistors and capacitors, assorted relays, etc. They have the replacement finals for the FT-101E but you have to modify the rig (change a couple parts) to make them work, as the newer tubes don't quite have the same specs as the originals.
Good luck!
Zack W9SZ