One product that contains this form of Bt is manufactured by Valent Biosciences and called Knock-Out®. It is available online from Gardens Alive. It is a liquid and applied to the soil. I have not seen it available in town. Follow the label directions. If you have a plant with fungus gnats in the container soil, do not bring it in the house. These little guys will spread to other soils in other containers if the soil has enough decaying organic matter in it.