I use xanthan gum. I'm not sure where you can buy it where you are; maybe a specialty baking shop?

It's a vegetable gum that's virtually carbless (all the carbs are fibre). About 1/4 teaspoon thickens a cup of liquid. Yes, it goes a LONG way! It's best mixed first with fat or oil, than add water (like a roux). The finished product (I made turkey gravy) looks and 'feels' more like it's thickened with cornstarch than flour, but that's fine by me.

Rachel