Ritberries are the answer. They are in season year around. Go to a store that has a good selection because you will need a couple of special colors.
Do not use the brown or black colors. They tend to go to red abnd purple undertomes.
You need one pack of Pearl Grey and one pack of Kaki mixed together. These two colors smooth each other out and duplicate the results I have achieved with walnut hulls.
Our walnut hulls in this region tend to go to black, so I sometimes use just the pearl grey and duplicate the natural results almost to perfection.
Mix in hot water, in a large plastic bucket (3-5 gal), and add two cups of salt. Let them soak overnight.
Use a test scrap first just in case. If you don't like the color you are only out a couple of $$.