Looking for contacts for this very special project.  To explain the project:

My Dad has a old Lionel HO (yes HO) steam engine.  Back when I was a teenager, the engine was not functional, and I took it apart and found out why - a plastic gear on the main drive axle was cracked, and instead of driving the main axle, would just spin in place.  The gear was removed and we attempted to find a replacement with no success.  The engine is still fine, but the gear has gone missing over the years.

It would seem to me that if a proper set of measurements could be generated, a replacement gear might be able to be made as a 3d print.  The gear is straight forward, hole in the middle which should press fit over the drive shaft, with simple teeth to engage the next gear on the outside.  Form the hole too small and repeatedly drill it larger until it fits properly.  (Maybe build a couple for trial and error.)

This project is not worth buying a 3d printer on it's own, but seems like a great use of the technology.  Who is available as a place to get this done, and what measurements would I need to get it done?  Or should I say, whom should my Dad contact - he still has the engine and is thinking of building a new layout of his own (maybe because of my participation here?)

Teaser:  I showed my Dad the article I have coming out in the Nov time frame.  He recognized the structure, having been there many times himself, from before I was born, until more or less modern times.  It got us talking about his future layout, and this old engine.