How about posting a picture of the broken parts? You may find a similar item made for another engine at Lionel's or MTH's website. You may be able to get them in brass from Precision Scale or Stevenson Preservation. Or they may be able to be fabricated from brass stock. Lastly they may be able to be 3D printed.
There are still folks who build engines from scratch. This is not the apocalypse that some make it out to be.
Pete