I would replace both worm gear and this gear to ensure proper mating. Not only pitch but addendum and dedendum must match.
Steel worm gear vs Bronze gear the steel will win. This is a designed failure.
I don’t believe in “Run in” The gearbox design is flawed. Running in? well that bronze material is only going to stay in the gearbox causing additional wear unless you remove and clean and re grease after a “run in”. I doubt the Lionel replacement is re engineered. Sorry I can’t help suggesting a source. I will eventually be in this situation i am sure. In the past My father would have machined a new set being master machinist.
