Your local lumber yard or roofing supply will have an item called "galvanized step flashing". These are pieces of flat sheet metal about 5"x7". I do not remember the thickness, but it was the same as an old perfect tank. Another name for them is "tin shingles". The last ones I bought (in the last year) were .29 each. At the local machinery supply company you should be able to buy 1/8" soft copper tubing.