Since there is an issue with the "N&W Class J 4-8-4 Northern" being trademarked by the museum that owns it, may I suggest the "N&W Class K-2a 4-8-2 Mountain" instead?
There were a number of Baldwin Class K-2a 4-8-2 Mountain's that received semi-streamling that made them resemble the Class J's. If you do a search for images online (N&W K-2a), or go to ( http://www.3rdrail.com/images/NW-K2-brochuresm.pdf ), you'll see what I'm talking about. They are very close in appearance, but not exact.
This would give us a nice streamlined locomotive that resembles the Class J without worrying about the trademark since it's NOT actually a Class J.
