You can buy stevia in most supermarkets under brands names such as Truvia, but it is mixed with sugar alcohols such as Maltitol or Erythritol, I make stevia sweetened chocolate bars (
discover chocolate) and use a bit of Maltitol to help reduce the aftertaste of the stevia but keep it ok for the no added sugar claim. The best place I think to buy stevia is online, such as eBay, if you can get it in the green powder that is best as it has nothing added to it. Or you can go to your local garden centre and buy it in plant form, then just pick the leaves off, dry them, and then use them as they are naturally very sweet! Stevia is definitely better than artificial sweeteners such as aspartame or sucralose. Hope this helps.