Have you ever tried pumpkin (it is known to ease constipation in pets)? I buy a large can of pure pumpkin puree, divide it into ~1/4-cup portions (~5g net carbs each) & keep them in the freezer. You can eat it plain or with butter or throw it into a savory dish or go sweet and make a pumpkin pie pudding: thaw one portion in the microwave, add some cinnamon & stevia & butter, stir & and heat it some more for a warm pumpkin-pie-tasting pudding. It is easier to apportion than a sweet potato and keeping individual portions in the freezer keeps it handy & fresh.