Go to a truck stop or big truck dealer, tractor-trailers use a big spring that hangs on a bracket on the back of the cab and has clamps to attach it to the air brake lines and
light cord.You may be able to make one of those work. The spring is about 1" or so diameter, maybe around 12" long or a little more. I probably have one somewhere but can't put my hands on it right now. They are also used under trailers that have sliding tandems to keep the air lines from dragging in the road.