The 4-6-4 Hudson is still in production at Rivarossi (now owned by Hornby). I'd e-mail customersupport@hornby.us and see if they have replacement motors available.
Golf Manor Hobbies is belly up. They did buy a lot of old Riv parts and I don't know who has them now. Since the Hudson is still in production, there's a chance that Hornby might have a replacement motor.
PM me. I have a contact that sells parts for engines. He's got a new set of drivers and a frame for my 2-8-8-2 that hit the floor while on loan to a club for a show.
to Hornby does not have any replasment parts for rivarossi steam engins that were made befor thay soldout to Hornby I was on line and phone with the head man seeing if thay had a motor . But thank all of you for answering my inquiry