A copper trellis made of old copper would look great in your garden. You have the plans and know how much copper you need, now you just need to find the copper. Finding the copper you need may be a challenge and require some ingenuity. Here are some pointers:
Metal Scrap Yard
In most cities there are metal scrap yards that buy copper from sellers. Many of the copper items they buy are old copper pipe which would work well in building a trellis. Call several in your area and tell them about your project and see if they have anything that would be right for building a trellis.
Companies that do renovations may be able to find some old copper for you. Often when a house is renovated the plumbing is updated to PVC pipe and the copper pipe is removed. A renovation company would know which houses were having this done and could refer you to the owner to purchase the pipe from directly.
Plumbers can be a great source for copper pipe. Call a local plumber and see if he can give you some leads on getting some copper pipe. In return you can offer refer customers to him or even to pay him a commission for the pipe that you buy.
Architectural Antique Dealers
Antique dealers that specialize in architectural elements like claw-footed tubs, old window pane, and hardware may also have some copper pipe. If they don’t they have some in stock they may be able to find it for you or point you in the right direction.
Online metal exchangers trade metals including copper. You create an account and you can browse the listings of the old copper. Sometimes these require a bulk purchase but some buys are for small amounts.
If you know of some abandoned older homes, especially ones slated to be demolished, in your area find the owner and ask if there is copper pipe that you can buy and remove.
Appliances like washers and hot water tanks that have been put out at the curb or in a landfill often have copper pipe in them. Don’t take copper pipe from air conditioners or refrigerators that have fluid in them as the fluid is likely to be polluting coolants that should only be handled by a professional recycler.
Antiquing New Copper
Old copper is expensive and can be hard to find in some areas. If you want the look of old copper then you might want to buy new copper and antique it. You can buy a kit with two sprays that you use to create an antiqued look. You can also just wait for time to take its toll. The copper will weather over time.
Wherever you find old copper be sure that you have permission to take it. Copper pipe is valuable so you may have to buy most of the pipe that you need.