Electro-magnets
I'll try your suggestions.
Since I posted I have had some luck modifying a Kadee electric. I added 4 heavy metal washers on each side and energized with 24 volts AC. It only works with HO scale size couplers but it works flawlessly....actually much better than than the original and it's totally hidden under the track. I think this is the ticket. I plan to convert totally to scale size couplers anyway.