I got a replacement C9-1 flashtube the other day from ebay seller "lights64". I had ordered the tube a few days before the old tube blew "just to have a spare", so for once in my life things worked out right! A few minutes with the soldering iron and the flash is working great again.
"lights64" is an excellent source for both older and newer style flash tubes, and his prices are great to boot!
In addition to my White Lightning "paint cans", I have six of the Photogenic Studiomaster S-200 packs. Despite their age, keeping them flying isn't as hard as you might imagine. The 2D21 trigger tubes are still easy to get and the 929 Phototubes (the 1P39 also works), while a bit harder to find, have been showing up on ebay. You don't "need" the 929/1P39 as you can always use any slave that can be attached to a sync cord, but they are convenient.