The baby foods can be found in the baby aisle. Some of them are quite nice, others can be a bit tasteless. The best tomato sauce I have found so far is the Weight Watchers Parmesan and Pesto Pasta Sauce: 175g (1/2 glass) has only 86 calories, 3g fat, 3g protein and 90g sodium.
Also, I am not sure if you are aware of this, but here is some info I got from Atomic some time ago on the subject of sodium:
"Do not drop the sodium any lower (than the recommended 700-1000mg). That is the level of sodium that is required for your health and this is true on all three diets, IG, FGD, and LE."