Bachmann 5 pole core motor for many Bachmann locos. This is just the core motor, and you will need to re-use your own existing worm gears or flywheels. These can be removed from your old motor with a bit of heat.
Mashima 1020 Flat Can 5-Pole Motor With Comet Models 38:1 Gearbox For 1/8" Axle
Single & Double Shaft 5-Pole Motor 12v dc For OO Hornby & Bachmann Steam Diesel
Hornby 5 Pole Motor Upgrade for Class 395, Eurostar, Railroad 43 & Pendolino