MODEL POWER 4-6-2 Steam engine

Try Northwest Short Line at Look for a motor with dimensions similar to the Model Power original. If you want a flywheel, consider a double shaft motor so you can mount the drive gear at the forward end and the flywheel on the back end so it fits in the cab which will provide the most room. Check out the NWSL page of remotoring notes for some good suggestions. Geezer

Seconded, NWSL is an excellent source, and they have loads of useful information. But you will have to do some fitting and fudging to install the motor. There's also the problem of gears - if you can pull the worm gear off the old motor, and the NWSL motor shaft fits, it will be an easy conversion. NWSL may even have a motor and geared driver set to fit, again, an easy conversion. Otherwise, it will be -- um, ah, erm, how do I say this politely -- a serious pain.
Oh yeah, the price will likely be about what you paid for the engine way back when. Maybe more.
IOW, unless these engines have great sentimental value for you, and you are handy with tools, I would not recommend remotoring them. But it's your engine, and truth to tell, I've done similar irrational upgrades and improvements on what would otherwise be junkers. Fun hobby, fixing old engines, isn't it? :-)