The 2-10-0 Russian suggestion is actually a very good choice. Tons of roads had them - and the USRA based their version off the originals specs. I'd buy one. No question - if scale is an option. Not only that, the motor block could be re-used for a generic 2-10-2 Santa Fe class. Over 2200 of those were built and used across a ton of roads.
Well, not really. The Russian decapod is not a large locomotive. It looks big, mainly because it's narrow boiler is fairly high off the frame.
The Russian's driver diameter is 52". Strasburg's ex-Great Western decapod's is 56". A USRA 2-10-2 driver diameter is 63". Depending on the Class, Santa Fe's 2-10-2's had either 57" drivers or 63" drivers. The Pennsy's N1s and N2s 2-10-2'a had 62" and 63" drivers respectively.