I usually find the parts I need from one or more of four places:
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.