Hi Jo, welcome aboard. Soy protein isolate is not known as a low-carb product, even though it's very low in carbs. Try to look for it at nutrition shops like bodybuilding type of stores, or at any supermarkets with a focus on vegetarian/organic products and you might find them. So protein products have unflavoured poder, which can be used on recipes.

There a good chance you'll be able to find it locally, and once you do, please let me know where you found it. I'm trying to build a database that will list such information and make available so people can do search by city/country etc.

Wa'il