Tonysmoke,
Riversidemodels do a kit which you can make into either a trad working boat or a pleasure style. But as Guy has said they all had different sorts of bows, and the riverside kit needs a bit of moding, the hull is around 4 ft and does make a nice model.However I do have the yard drawing (plan) of a steel motor working narrow boat cir 1931 published by the Inland Waterways Models Company in 1979. The full size hull was 70 ft, and the section of the drawing is around 35 in. If it is of any use, PM me your address and I'll stick it the jolly old snail mail
Phil