The small Fleischman one that a previous poster mentioned do occasionally come up on eBay, but it uses the n- gauge base which is a lot easier to come by. I used one and altered the deck top for oo gauge, (Playcraft ramp/bridge section is handy for this) and if I remember correctly it scales out at 45 foot, which was a size the Midland Railway used in their roundhouses (my future layout, if I ever get my finger out), and is just right for 0-6-0's.