Yes the Weldon parts are quite hard and amazingly the manual says that after the tool wears some you might need to increase the air pressure! Wear, what wear?

I've thought about the machining
If I'm starting with a solid I could turn the outside between centers, or start with an extra length piece.
If I start with the bronze piece, I might be able to grab the inside of the hole. I'd probably need a way to support the outboard end; rig a plug with a center dimple.
I have a tru-set six jaw that should work for the hole. My lathe is CNC'd so I can take a zillion shallow cuts to bore, or set up the steady rest. The bushing is only about 5.5" long, but these are soft materials.
Later,
Ozzie