If you want to check out the safety of the conditioner you are using, you can look it up at the Skin Deep cosmetics safety database. You can also search for low-toxicity conditioners. When I tried to do that, I found stuff that looked really benign, but cost $20 a bottle, plus shipping, and I wouldn't be doing anything to avoid buying bottles and shipping water around the planet.
So I looked for conditioner or hair gel recipes on the web. There are some out there, but a lot of them use the same chemicals that I'd prefer to avoid. There was one that worked great -- boiling flax seeds in water to make an amazing gel --but the result goes bad in less than a week and ends up smelling like rotten eggs. It's worth considering doing that and keeping it in the fridge to prevent spoilage, but I wanted to see if I could make something more convenient.
It turns out that this formula also has something of the same problem--it spoils eventually if it's not refrigerated--so unless you want to add preservatives, you need to make small batches, or keep most of it in the fridge. But it works well--as you see in the comments, some people swear by this formula.
Several comments also suggested aloe vera juice. You can buy that in a bottle or grow your own. That's also likely to have the problem of needing preservatives to last without refrigeration, but it seems to do a little better in my limited experimentation as far as keeping at room temperature.
Step 1: Obtain the ingredients
2/3 cup water.
xanthan gum and guar gum: 1/4 tsp each for gel; 1/8 tsp each for conditioner
1 tsp canola oil
I got the xanthan gum and guar gum from the bulk section of my local coop grocery store. They get it from frontier ; you can use their store locator to find a local source. You can also order direct from Frontier (both gums are in the cooking and baking ingredients section ), but you'll need to buy a 1-lb bag which is probably a lifetime supply for your entire neighborhood. You can order smaller quantities from Organic Creations , one of the few sources of soapmaking supplies that has mostly nontoxic stuff. Update: here's a source of really cheap guar gum but you need so little of it that a local bulk bin is the best option if that's available to you.
You don't really need both--they serve the same function (thickening, emulsifiying, lubricating), but they are supposed to work best in combination. If you want a vegan option, you might want to go with guar gum only. Xanthan gum is sometimes (particularly in the US) made from whey. I personally feel OK about utilizing whey which would otherwise likely go to waste, but if you want to be sure to have nothing animal based, you can simply go with guar gum, which is plant-based.
I don't have any scents in this--I prefer it that way--but you can add whatever scent you like. Experimenting with different scents can be fun. Soapmaking supply places have lots of wonderful scents available.
This is a pretty small quantity. One reason for that is that it doesn't have any preservative in it, and it's all food ingredients, so it will probably go bad in time. I haven't had trouble with that, but I haven't left any sitting around for more than 2-3 weeks. You could make larger batches, and keep most in the fridge. But you may want to start with small batches anyway so you can tweak the recipe for your hair.
You can read more at the end about how I picked these ingredients, other options to consider, and how to adjust the recipe according to what you want it to do.