I rarely feed my dogs commercial treats, usually just homemade or out of the fridge snacks, BUT.. I like the idea of a grain free cookie once in a while, and so do they.. and I opted for NOW! grain free treats.
You COULD make your own homemade grain-free treats as well..
P.S - I think your Shiba will like the Pacifica from Acana, for some reason, Shiba's really LOVE fish. I've used this one in the past as well, and although I dont feed kibble too often (my dogs eat a raw diet), my Shiba loves anything fishy - he loved Acana Pacifica when I fed it, and when I do feed kibble occasionally for convenience reasons I opt for something with fish for him, and he absolutely loves raw fish, and goes bonkers over it compared to any other raw meat or kibble.