The Kangal has been chosen due to the success protecting against Cheetahs. Nigeria suffers heavy losses of livestock, pets and in some situations humans. The Kangal is chosen for it's fierceness and for it's compatibility with humans and livestock. Article warns of being careful of claims of Kangals that are "cheaper". Bottom line is there simply is not a lot of Kangal puppies available worldwide. The breed is rare and Turkey goes off and on banning the export of their national dog.
Read one of the articles here on Kangals in Nigeria program.