I just got a message from Serbia of a web-page for tubes: www.tubes.rs.
The owner of this page is ex-pirate called Radio Columbia from Pancevo, near Belgrade. He was active pirate for many years on MW in the beginning of 90's.
He has been collecting vacuum tubes for 25 years and he owns today about 25 000 tubes (!), some of them unused!! In his page there are many photos and also old schemas of tube-transmitters for FM. Very nice page - and collection!
Perhaps he is also selling tubes, if you are interested (There is his e-mail).
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Glowing tubes are very beautiful !! There is no doubt of that! It was fantastic view when I visited Greek pirate station in Larissa-city 3 years ago.
I saw 5 kW transmitter in action. It was Radio Parizionos. (However, I do not know what are the tubes in this transmitter >>> Click for larger version) - More photos