I can actually think of a fairly simple way to make this work: Consider that maglev trains are simply fancy linear electric motors, and that using a brush is always an option.
My proposition is this: Use wound electromagnets with an iron core attached to the train. Then power the rails with a salvaged PC power supply; I've used power supplies for high current applications before and the 5V line can handle upwards of 30A. Then use brushes: If you can manage to find a -5V supply as well, you could use 3 rails with the train contacting them by brushes. The left rail would be at -5V, the right at 5V, and the center connected to ground. One side of the electromagnet would be permanently connected to the ground brush; the other would be connect to a brush on both the left and right sides of the train. The rails on the left and right sides would alternate, so that when the train was over a north magnet the magnetic field of the electro magnet would be north, then when it moved to the next segment, the rail would be the opposite polarity, and so would the field created. It would be up to you to figure out the right amount of offset so that the fields switched such that you would repel off the end of a segment and be attracted to the next.
As for the construction of the interface, I'd use a thin sheet of aluminum foil for the rail, and a metal tab for the brush, with one end fixed to the train, and the other contacting the rail. A spring half way between would provide pressure against the rail.