I would suggest solid gold "Just a Wee Bit" dog food, made for small breeds. Solid gold is one of the oldest holistic food out there and is pretty much used amongst some of the more serious dog show dogs.
here's the link from petco
http://www.petco.com/product/15039/...aintenance-Dog-Food.aspx?CoreCat=OnSiteSearch
here's the link from petco
http://www.petco.com/product/15039/...aintenance-Dog-Food.aspx?CoreCat=OnSiteSearch