Stevia is your best bet, being a plant. However in powder form it is brown and might discolour the cookie - but being c. chip it should be fine. Follow the instructions as Stevia is very sweet compared to sugar.
I don't like using artificial sweeteners, so if it were me, I would try to find a recipe that uses natural substitutes like dates, applesauce, or bananas--assuming you can have natural sugars. I'm not familiar at all with sugar intolerance, though.
Anything sweet can replace sugar in cookies. Honey, Golden Syrup, Maple Syrup, Agave Syrup, Splenda, Stevia, Corn Syrup, Brown Rice Syrup, Sorghum, really anything! Keep in mind stronger flavored substitutions will add flavor to the party. And that's not always a bad thing. ^-^
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