New steam power

The thread on newly constructed steam locomotive power for the Loop has aroused my curiosity.
I know there are several reputable repair facilities that can do complete rebuilds of just about any steam locomotive in existence.
But what companies have the capability to build from the ground up and new, modern steam locomotive, whether standard or narrow gauge, that is not a tiny "theme park" sized locomotive?
To phrase my question differently, who could build a replica of one of the Uintah/Sumpter Valley articulated locomotives? Who could build a replica of a three truck Westside style shay? A K-28 or one of the White Pass 70 class 2-8-2s?
If anyone knows a company who has this capability, I would be interested in learning about it.