You can get low carb canned food at Walmart. Many use Friskies Pate, 9 Lives Pate, Fancy Feast Classic and even Special Kitty Pate is fine. Just be sure to get only the Pate type and not the ones with gravy. Also to save money, pick up a Relion Glucose meter while you're there. The Confirm or Micro take less blood, and the Prime takes a bit more, but the strips are cheaper. With your own glucometer you will be able to keep your kitty safe and save money because you won't have to go to the vet for curves to measure his glucose. You may want to contact Diabetic Cats in Need (see the link Alexi provided above)They can help with insulin and meters as well.