Hello!
I have made headers and mufflers from pieces of old shopping carts, luggage racks and just about any piece of pipe that is about the right diameter and has a bent section that I could cut and piece together. I line them up and weld them. If you do not have access to welding equipment, cut and mark everything accurately and take it to an auto repair muffler shop or a welding shop.
Hell, ship your parts to me and I'll weld them for free.