I've been using "Royal Canin Sensitivity CR" (chicken and rice). It worked wonders for Toby's tummy and diarrhea... I get it from my vet.
He's also been eating the Royal Canin Sensitivity dry version (which is duck) and just recently I've been trying Hills prescription d/d (lamb) (the canned stuff). All of these seem to work fine for his stomach, although I'm having a lot of troubles getting him to eat the right amount.