The original 2SC2166 and 2SC1969 finals were originally made by Mitsubishi. The 2166's can still be found on the 'Net in limited quantities, but the 1969's are pretty tough to find. For every genuine 1969, there's probably about 30 fakes. Best to get pulls from a junk SSB radio to ensure you're getting the real deal.
Mosfets are cheaper to get, and aren't too terribly difficult to replace if you have a little bit of electronic know-how and some soldering experience. I have a thread written up on how to convert the common AM/SSB boards to Mosfet finals, like the MB8719 and D858 chassis. I also have converted the PLL02A SSB boards to Mosfets as well, but haven't updated the thread yet.
P.S. Just remembered, some Uniden Washingtons have the NEC 2SC1306/Mitsubishi 2SC1969 pair in them, if yours has this pair in the radio, you can sub out the 2SC1306 with a 2SC2166 and it will work just fine.