Robert,
I think the folks who are The Leadville Shops (Dr. Stears, Bill Meredith and Doug Junda) produce brass detail parts, laser cut rolling stock, trucks and lettering sets to satisfy their own modeling interests.
They underwrite the associated cost (which may be substantial) by selling surplus items to those lucky folks who share their interests. Kind'a like the Blue Bell Ice Cream slogan back in Texas:
We eat all we can and sell the rest!They have just added cast resin DSP&P Eames vacuum cylinders in both Sn3 and On3 to their detail list, so someone there is interested in early 1880s DSP&P. They also have an On3 Colorado Central Porter Bell locomotive project c1880 on the site; it appears to have a Nesmith style stack.
Go to The Leadville Shops website:
http://www.theleadvilleshops.com/. Click on "More" and then click on "Contact" and email Doug Junda. If an O scale Nesmith is available, he will let you know.
Jim
Jim Courtney
Poulsbo, WA