Machine the hub lead in surface, taking off a few thou, concentric to the wheel location diameter.
Extend this lead in and take off the rusty wheel location diameter up to the spacer face.
Make a sleeve a few thou over-size and the length of the wheel location diameter that can be pressed or shrunk onto the new lead in face up to the spacer face surface on the hub.
Machine the diameter of the sleeve to fit the wheel inside diameter.
It is important that every thing is kept concentric and square to the disk mounting face.
Naturally you need the lathe and the skill or know someone who does.
I never said it would be easy.

Or you could laser weld the lead in diameter for 5 mm from the existing wheel locating diameter slightly over the wheel location diameter, you would not need 100% coverage.
Then machine the weld to the wheel location diameter.
Laser weld does not apply much heat, three or four beads of weld around the circumference would be ample. You do not need arc welding, too much heat.
This is a simpler method and probably best.