Kirkville Locomotive Works
I just randomly found this site via Ebay, then checked out the Facebook site. I must say this guy is quite impressive. His models are 3d printed, the quality and the variety is good.
If you're looking for a model not made by the big companies, he'll most likely have it or is able to produce it. If you're looking for a specific model to modify, detail, paint to suit your preferred prototype this is a great way. If you're after a Alco 636, EMD BL-2, HH600, Boxcab or any other prototype this is the place to go.
If in doubt, slab out!