Innova Small Bites is a good food, and the kibble size is small. Artemis Fresh Mix for Small breeds was a hit with my picky eater. And the kibbles are also small. But the #1 food for my picky eaters is Timberwolf Organics. Snickers turned his nose up at everything until I tried Timberwolf.
I guess it's just trial and error with the picky ones. Good Luck!