Where can I buy shikakai (acacia) powder in the UK?

or any natural shikakai product (e.g.shampoo) .. I don't want to buy online as I like to see any product i'll be using on skin/hair firsthand, so i'm looking for any shops or supermarkets that you guys know about that sell acacia powder, i live in the manchester area so anything local would be great, thanks in advance ;)