If you can't get to a specialty store to buy Canidae or one of those, Petco sells Solid Gold which is also a 4 or 5 star food according to
www.dogfoodanalysis.com Generally according to that website 4 or 5 star foods are recommended for yorkies. As long as you do a gradual switch, your furbaby should be fine. We homecook for our dogs and change the recipes every 3 weeks or so.
My mom feeds it to her maltese...