aluminum for your local hardware store. Flashing material. Wood veneer the easy place to start is a cigar store for some free spanish cedar from the bottom of a cigar box. YOu can always order picgard material from Grizly and a pack of dyed wood veneer from woodcraft.
I got a heck of a deal on 23ga aluminum on ebay...stock for years!! Copper is hit and miss given it's value. Picked up some great wood veneer on eBay 5x7 sheets, about 50 of them for 8 bucks!