Looking for a Great pyrenees sheep dog for sale?

Iam in the FFA at my school and this lady wants to borrow our sheep and put them in her yard to eat her grass, but my advisor looked at the place and said that wild dogs could come in and attack the sheep, so he wants to get a dog to protect them if we let her borrow our sheep. So he asked my sister that if she found a great pyrenees, because there supposed to protect sheep, that he would help pay for it and that we can keep it at our house and we can bring it to protect the sheep at our farm. So anyway I was looking online but all they have are puppies, and we want one thats already trained to protect the sheep, so if you know anyone or a website that has trained pyrenees please let me know oh and i live in california.............Thank You!!!!