I have made black walnut tincture before and I find the way he is doing it very interesting and will definitely try it this year.
Making it yourself will safe you a lot of money.
How to take it: Hulda Clark (PDF)
How to make black walnut tincture. I added olive oil to the surface of the tincture and find that batches can last for years and remain light green with the oil barrier when stored in the refrigerator. So far, I see no one else employing the oil top barrier for preserving black walnut tincture.
Black Walnut trees can be found in the eastern US and Eastern Europe. These Black Walnuts I am using are native to California. Be sure to use gloves as this stuff stains and will also stain your counter top if not careful. Black Walnut hulls were once used as ink and hair dye.