You might try this website:
https://www.powersourcing.com/sf/mulchcolorant.htm
If you don't find one listed for your area on the first page there, click on their link for
More Mulch Colorant Suppliers. It will take you to a page where you can enter information about your local area.
I have no personal experience with the website or any of the suppliers they list, so I can't offer you any guidance in that respect.
