The Nokota Horse Conservancy currently has Nokota Horse 2007 Benefit Model Limited Edition in stock, although the model is officially listed as "Retired" at the Breyer website. The actual Nokota horse is a breed of mustang based in the badlands of southwestern North Dakota.
As a follow-up to my original post, I decided to attempt a repair of one of my broken Breyer horses. As you can read in the first part, I did not have a lot of success with this! I went to the store and bought a fresh bottle of nail polish, and decided to try again. And again. All in all, I have made three attempts to repair Sagr's tail, with no success.