Internally on a hub?
Where are you loudhornsrule? Did you find an alternate? How much would you be willing to pay?
A tapered bore with a key way would NOT be a difficult group of features to produce. A shaper would make the keyway a breeze
That would be a broach. Need a tapered plug to press it thru.
Sorry. I was reading this and saw where you are from,and thought you mite be American living in Europe.