I have a pinball machine that needs a specific spring, but the usual sources
have to custom make them, resorting to a minimum quantity (usually 500).
The spring is of compression-type. It is much fatter in the middle than on the
ends. It looks like 2 cone springs back to back, but there are no welds
evident, it is one whole spring. When compressed it forms a nice thin ring (all
the coil turns come together).
Anyone know - What kind of spring is this? Any known off the shelf source ?

Thanks in advance.
Marcel