[Claude Paillard] makes his own triodes (google translated) for short wave radios. The site doesn’t have a lot of details itself, but links to entire books on the history of radio tubes and manufacturing of them.  [Claude] takes us through the entire process of building a triode in a 17 minute long video. Even if you aren’t into them, this is fascinating. From the looks of it, several of us might only be a pump or two short of being able to cobble one together.

[thanks Dieter]