Three days later: alex_holden has a broken Magic Santa Monorail Tree Ride from eBay.
[spot snapped-off flimsy bit of plastic]
[root in scrap pile for a suitable bit of steel]
[cut, bend, file, hammer, superglue, reassemble]
[place on section of track, connect power]
[Monorail Santa screams "HA! HA! HA!", runs over alex_holden's fingers, and falls off the end of the track]
alex_holden has a monorail that goes round his Christmas tree (or will do when he gets around to putting it up).