The bad armature pictured on the bottom is from a Eureka model 10. It was the first Eureka model to have a cooling fan. In contrast the Eureka model 9's armature is a little longer and has no cooling fan, but I've found that you can also use it for the model 10 - it works just as good. Pictured on the top is the before mentioned Kirby omega armature (1973-1976). The Eureka's is from (1927).
The Kirby armature is pretty well worn. The picture that you say the "magnets are heat warped and fractured" is not that at all, the damage was caused by someone not properly inserting the fan removal tool in the armature to hold it while unthreading the fan. Those armatures are still readily available, check eBay or go to www.hescovacs.com and purchase one there.
Your right, when I got the omega, I had to replace the armature then - when I was restoring it, but in light of what you said - I see it clearly know. What kind of person could do that. Oh calamity, what is the world coming to!
Wow - that thing sure has some miles on it!
Almost looks like it was grooved to begin with, as I had not seen such severe wear, especially rounded at the edges. Cool picture - good luck in seeking a replacement.
Reminds me of the wheels of that D50 you had sent to me a while back. The holes were so worn it looks like it was pushed 100k miles around the house, maybe by a child? Motor had negligible wear and new wheels were installed.