Hi Charles:
Don’t know if you have found anything but I have a similar project underway and located the original plans for Endurance in the National Maritime Museum. A little pricey for us Canadians but purchased them anyway. The Scott Polar was also a source of info.
I also purchased a copy of ‘South with Endurance’ by John Hurley, great photos for details of the ship.
Hope this helps, good luck with your model.
Bob