Thanks to the generosity of another VK member, I have a 21FJP22A with good emission. It arrived yesterday, in my homebrew CRT box that I shipped to him empty. He popped in the CRT and sent it back, and it arrived here in fine shape.
I haven't tried anything on for size yet, since the cabinet is completely disassembled, but I guess some people would cut a notch out of this retaining ring to avoid fouling the 2nd anode lead on the new CRT.
It may be a while before I get to try out this CRT with the chassis. During our remodel, my workshop is packed into 100 boxes and temporarily piled in our new garage, which doesn't have power yet. Our living quarters are so crammed with overflow that I had to unpack the CRT in our front entry -- and then clear away all the mess before dinner guests arrived.
Phil Nelson