Preservatives that don't suck for conditioner

So the world of no shampoo has been great for me and my husband. But not so much for the other members of our household and various friends who test out my "odd" beauty things and habits. I have a shampoo bar recipe that I enjoy but I need a conditioner that is liquid. I didn't think this would be a issue until the nature of natural preservative became apparent. They seem to all have conflicting answers, are overpriced, have no real evidence that they do what they say or I need to use a combination of 13 rare hard to find MacGuffins to kill all the bad things that could lurk in my conditioner just waiting to pounce. I'm hoping to find something effective for at least 6 months, shelf stable at room temperatures, ecologically ok, preferably natural and affordable! I'm not sure if there is a easy one shot cures all solution but I thought permies would be my best bet.
Thank You!!!

I rinse with lemon juice, too balance the ph, then towel dry, put a few drops of argan oil or hazelnut oil in my hand, pat it to both hands, and run it through my hair. That's it.

Like Carla I like lemon juice but also use vinegar.

Lemon juice is good for blondes and vinegar is good for other hair colors.

I have read that mashing a banana, mixing with honey, and egg and some milk is good though I have not tried that.

I have also read about using coconut oil, again I have not tried that.

I think this one will depend a bit on your hair type. I have very straight thick hair with a tendency to oily. I use no shampoo now and don't need conditioner at all - my hair is healthy and shiny. I think it is probably more useful for finer, frizzy or curly hair particularly long hair that might have a tendency to tangle.
So I meant to say - no conditioner at all is an option for lucky people like me, sorry to not be more help Sam!

I'm a natural redhead, and used to use vinegar, but hubby swears the smell doesn't dissipate, and he hates it, so I switched.

I'm looking for something that is a bit more stable and doesn't need to be mixed up everytime someone in our family needs conditioner. I don't personally use conditioner or shampoo. A bit of coconut oil on my ends is normally all I need. The young adults and kiddos in the family are the ones who want it. It also can't be refrigerated as they won't use it if it's not in the bathroom, ask me how I know :)