ya a 50' roll of new tubing,it will come in a tight coil and makes it easy to bend.
then you'll be like me with enough left over parts and pieces to make 20 or 30 cloners
and my parts suppy stores WON'T buy back my extras

or try this cut a piece long enough to make the circle,plug one end fill it with water put it in the freezer and freeze it solid. then bend it to your circle,in the bucket
let it thaw out and it should stay bent without kinks
thats how they make the bends in thin brass trumpets and trombones without kinking them