Repair Technician, The motor runs on 5 volts not 3 volts and you can buy the motor from MTH. You do not have to buy the complete smoke unit. Part number BE-0000041 for the fan motor.
GT, what PS2 steamer do you have? Most PS2 steamers have the PS2 board in the tender. I would say your best bet is to get your PS2 board to an MTH tech that can put it in his test fixture and check the board outputs. I see where you live and you should be able to get Bill Lucas to do that for you. If your board needs a component repair, contact forum member GGG. When you ran your motor on 9 volts, did you do it with both wires unhooked?
One last thing you can try is to pull the 4 pin connector from your PS2 board and plug it back in. That 4 pin has two wires for the fan motor and two for the heaters.