First off a good reference for scale.
S scale is the closest, if you can find it since it is not a popular scale. You can do it a lot cheaper. The ik folks have been using holiday trains for ages. They work since terrain is representative and just a part of an actual scale train will cover the majority of the board. Another option that is cheaper is to use some of the MDF kits that are available such as this one.
For me cheaper that I can dress up is always better than completely accurate. Hope that gives you some other options.
Snitchy sends