Go to your local chemist, check out Carob Health. They have 25-100g pots of the stuff, which lasts forever as you don't really use a lot at a time. It's just pure Stevia without any of the crappy fillers.
For some reason my local chemist sells the 100g bottles for $7.95, where as the 25g tiny bottles are $30. Exact same stuff, I checked to be sure.
White bottles with Red/Green/Yellow label.
-Mitch.
p.s - I'm very tempted to take up that challenge Power Sports. I haven't had a Mars Bar in YEARS. But can we make it Snickers instead, they're way better!