Plumber's Tape
This stuff is used by plumbers to hang water pipes under the house. it is basically a strip of galvanized steel, perforated with alternating large and small holes. There is a copper plated variety that I like to use. Bending this stuff is tricky in that it will break if you bend it back and forth at all. Luckily it isn't too expensive, and it is available at most hardware stores. One note on the copper plated type: some states may not have a building code requiring it to be copper plated, and availability might be limited. Home Depot usually carries both types, and their brand (Oatey) is thin and patinas well. Lowe's has a shinier softer product, that is fun to use too. A very versatile material, I use it for my book spines and sometimes for the covers. I have even seen people make entire sculptures with this stuff.
Click either of these pictures to go to an online source for plumber's tape. You should be able to find it at your local hardware store too.