You don’t need it. Shampooing is one of the worst things you can do for your hair. It strips it of all its natural oils, drying your hair and damaging it, while at the same time stimulating the oil glands in your scalp to produce too much oil in an effort to keep up. The end result is dry hair and oily roots, prompting you to wash even more often.
Professionals (such as models) who must have beautiful, healthy hair will go days or weeks without shampooing, only washing their hair immediately before a shoot or other event.
Wash with baking soda and lemon juice. First make a thin paste of baking soda and water, pour and massage it into your scalp. Let it sit for about 10 minutes if you can. Then rinse with lemon juice diluted in water.
If you are used to using shampoo every day or every other day, it could take a couple of weeks to see good results. Your scalp will need time to adjust and slow down on the oil production.
You will still need to condition your hair some. I recommend dabbing a small amount of coconut oil on towel-dried hair. No need to rinse it out. You can use olive oil, if you prefer.