Got this idea from another forum. [Didn't see Stan's post above before I posted this]
A laptop power supply. An old Toshiba laptop I had that no longer worked has a power supply with the same size barrel connector. It puts out around 19 volts. I tried it and it works just fine. It is rated at 1.5A.
The voltage isn't as steady as the Lionel, but it uncouples and handles the Lion Chief engine very well. I don't think my daughter and her husband want a large transformer in their apartment. As it is they stand the Fastrack layout against the wall (using small office clips to held the sections together. Even if I pick up a new laptop power supply rated at closer to 18V it is still smaller and cheaper.
Also, I have an HP laptop power supply rated at 18.5V and 3.5A with the wrong size barrel connector. I could solder an appropriate connector on it if you think that is better.
EDIT: Are the couplers on those new sets awful? They don't uncouple and couple very well. But they do separate.
SORRY STAN: I actually didn't see your post before I posted this. I saw it on another forum, tried it, and posted. Thanks for the suggestion (and every one as well).
John