During Long Island's defense contractor and space program hay day LNL was smack dab in the middle of it on Robbins Lane in Syosset. They used to have an extensive tube selection and still may. I think least one fella there is radio savvy
( Lionel ). I don't think they are particularly inexpensive but having what you need right there is a big plus if your in the area.
Blah blah blah, I hope this helps someone
FWIW, here is the link:
http://www.lnl.com/