http://www.yorkietalk.com/forums/yor...itionists.html
If you want your Yorkie's recipe to meet AAFCO or NRC standards (dog foods are expected to meet AAFCO), then it's almost always necessary to use a board certified veterinary nutritionist (a veterinarian who is also an animal nutritionist).
A few of use use Dr. Remillard out of Angell.
Petdiets.com and balanceit.com have recipes that you can get pretty cheap that would be balanced. They are only for adult, altered, and healthy animals though; otherwise, a consult would be necessary. When possible, if buying from one of these sites, I'd try to go with an option that says lower fat.