IAMPETH -
The International Association of Master Penmen, Engrossers and Teachers of Handwriting- has a variety of antiquarian texts on the subject available for download on their site. They are PDF's, and most likely in unfriendly sizes. The one I grabbed was about 8.5x5, wide but short like a Zaner student's book.
http://www.iampeth.com/books.php
-MJ