Walmart, Petsmart, Petco, Amazon; They're everywhere, and come in too many flavors! Inaba (Japan) seems like a quality company, and Churu is well- reviewed (it's protein puree, high moisture, nothing terrible in it).
My 12 y/o buddy just started eating them (chicken flavor), and goes alarmingly nuts for them. Great for adding water to diet, sick days, meds, etc. (Nulo, Tiki Cat, others also make quality puree pouches.)