Erm, well I'll be at my shed tomorrow night so can grab it then, it's not the prettiest, I'll check it over when I grab it, but can take it to Atec or whatever really, up to you.
A stainless shaft wouldn't be tricky or particularly expensive. We could always up the wall thickness slightly to bring up the strength. We could bore out the old shaft from the arm and tig in the new one, or could most likely mill a stainless arm to go with, again considering the thickness to allow for extra strength. I'm sure a good stainless one would be much stronger than most of the rusty old steel ones I see!