If just baking soda and water was just not attractive enough for you to make the switch, try this instead. I vacillate between both of these, depending if I run out of one or the other mid-shower ;) This came from Homestead Community Post's website, though I do not remember which member donated this idea. I am going from memory and from my own tweak, so it may vary from the original post somewhat.
When my garden was up and running, I harvested as much herb as possible and filled a mid sized pasta pan with rosemary, mint and lavender cuttings. I covered this with water and boiled for 15 minutes. I then put a cover on it and let it cool to room temperature. While this was cooling, I poured household borax into a rinsed milk jug until there was about 1" at the bottom. When the tea was cooled, I strained this and poured the 'tea' into the jug and filled the rest with water. This jug was sloshed around until the borax was well incorporated; it will not totally dissolve). This sat overnight and was ready for use the next day. Essential oils are optional. Pour it into smaller squirt bottles and use as a shampoo rinse. Scrub your scalp well with this formula and rinse well. Your hair will feel super clean and the herbs will bring health to your scalp and hair. Note: If you have light hair, use chamomile instead of rosemary to brighten your hair. The gallon lasts a LONG time! Pennies per wash :)