I had no idea that shampoos contain salt! Or that it is a problem. I use Faith in Nature shampoo, no SLS, but they do contain sea salt. Green People shampoo does not use salt, but I have not tried them. I use Green People sun cream, really good, so I would be happy to use their other products.
Faith In Nature often have offers online. They are usually about £5 for a 250 ml bottle. You can also get them in Oxfam, I got a few half price last week as they are getting new lines.
I buy Green People online. Waitrose often have it. They are more expensive than Faith In Nature.
after my keratin kit I used sainbury's kids shampoo in cherry almond, its good, smells lush and is CHEAP! there are very few on the shelves without sodium chloride (salt) so if you want a posher one buy online.