I accidentally gripped hard the flanged driver wheel with the eccentric steam rod and the tiny eccentric rod (kind of shaped like a tiny "Z") snapped in half.  So crushed!!  Tried gluing it but it didn't hold for a day.

I removed the entire assembly and looks like the spare parts store only sells the assembly in black or red. 

Would it be possible to just buy the valve gear assembly:
https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=70_78&products_id=7696&zenid=q8cvaufb3k3ugihdo4nioqc4r4

However I don't see any screws to enable the replacement to the wheels or to the green plastic piece, just pins and riveted heads.  Sort of confused how I can fix.