Siding: Cypress siding
Unlike pressure-treated lumber, cypress contains no arsenic salts, making it both environmentally friendly and safe for residential applications. North Carolina-based Buckley Lumber sells cypress lumber wholesale, with a 1,000 board-foot minimum on orders.
The good news is, they'll help you "do the math" to calculate how much lumber you need to order. Or, if you're good at ciphering, there's a conversion formula at their Web site.