It depends where you live. If you are in the UK you can buy it from an online store called www.mariposa.co.uk
The Urtekram range is available throughout Europe but I don't know if you can get it in the US. I'm sure there must be somebody making 100% natural soap in the US.
I have included a link about the Urtekram soap. They are an interesting company. Sometimes my Acne can be irritated by shampoos and conditioners round my neck and jaw line (I have long hair)so I swap to their shampoos and conditioners for a while as they too are as natural as can be and cause the least possible irritation.