Getting more horsetail from the Milky Oats Challenge?

Does anyone know how to get more of the ground horsetail that came with the milky oats challenge? The challenge helped me moderate my weight by eliminating cravings and gently, healthfully lowering my appetite. (I'm not badly overweight but could stand to lose a few since becoming menopausal. You know the story, ladies!) I LOVE to eat and the horsetail helped ease my mind/body away from food just to the point at which I had no interest in consuming excess calories any more. It was literally like a miracle. Is there any way to obtain more of that wonderful horsetail?