Yeah, it exists, but it might not be easy to find. I think the filter queen equivelent is in the link. Yes, it is expensive. the newer Royals had those kind of brushes too, so you could find a used one at some point.
The lower wand is just the standard lower wand that would have come with any older Royal, Filter Queen, or Royal private label machine. Again, it might take some time to find one.
Your power tank is one of the early ones, before they released the gas pump hose handle and discontinued the whole curved wand thing. That might be why you are having some trouble.