I'm not sure if it is available in the USA but I use a brand called Logona. I think it is German.
It is 100 percent plant based though not all of the colours are just henna, some of them have other botanical things and I think there is coffee in some of them. I
It is a very well known company for natural make-up and skin care too. It is the closest thing I have ever found to natural hair dye - I've been using it for about 4 years.