My first thought is the Parts Shop, right here at this web site! If you value this tech forum, support the PartShop, or at least give them a chance to give you a price quote! If they can't help you, I'm sure that members can direct you to other siurces.
Be forwarned, leather is not cheap. I think the common cars start around $500 each front seat and around $1000 for the back seat. Plus installation. It is recommended to do all seats at the same time to keep the same dye lot and exact color match. I would also recommend new padding at the same time, especially for the drivers seat.