Well, I was curious about the outcome, but I thought this might be it... Now that you've said you're through with this idea, I'll jump in! Like I said, I love a good experiment, even one that seems like it's been done a thousand times. I applaud you for trying your idea out, even if it ended quickly!

Soaproot and Soapnuts are two plants that foam on their own (they contain compounds called saponins) and create a cleansing goo. Soaproot is found in the western U.S., and was used by Native American groups as a cleaning agent long before Europeans arrived. I work in archaeology in California, and come across soaproot (and whisk-type brushes made from the fibers) everywhere! You might be interested in this article on making shampoo from yucca, which has similar properties.

Soapnuts are something I'm just learning about. My friend Andrea the chemist (her blog has tons of cheap DIY stuff, by the way, so you might like that) introduced me to them, and they are included in her current shampoo bar, this one. You should poke around that whole website, it has a lot of "low ingredient" items that you might find interesting, and they're more affordable than most hair/body products I see in stores. Those $2.70 samples last for over a month, for me.

Lastly, there are a lot of simple ways to clean yourself that are cheap and may seem modern, but have really been around for a long, long time (maybe not since Ancient Greece...). Baking soda is a great example. CGers galore use baking soda to clarify their hair, and I've seen some folks list that as their only "shampoo" method. A rinse with apple cider vinegar is also popular, and vinegar has definitely been around since even before the Greeks. You could experiment with adding herbal teas to ACV to make a rinse that suits your hair. Some light oils (not mineral or petroleum) like jojoba, olive, coconut, etc. could serve as conditioners. A lot of these items continue to be readily available in stores not because they aren't old, old ideas, but because they work and people have kept using them for dozens, hundreds, or thousands of years.

I bought my castor oil from drugstore.com, by the way. It's this right here by NOW Solutions, and it's a large bottle. I mix it with coconut oil two times a week for deep treatments, and I also apply it to my eyebrows (which thinned out for health reasons!). It absolutely made my brows grow back faster. I can tell because it has been a pain in the *** to keep them shaped since I started using it nightly. This bottle will definitely last me a while.
I sort of blog
I'm mostly away doing field work through mid-May.

Hair: curlybob, fine, dense, low-po, big waves/ringlets (2C/3A)
Co-Wash: Nature's Gate Herbal Conditioner
RO: YTC Carrot, Aubrey Organics GPB
LI: BS Shea Soft Styling Cream (HG)
Styling: KCCC, Garnier P&C Gel
1xWeek: low-poo, gelatin PT or Joico K-Pak
Hair Likes: aloe, coconut oil, humidity, protein, long walks on the beach