It was a real compression coil spring from a real hardware store. Most real hardware stores have a spring department with around 50 or so common types of springs. I picked one that would fit the bore and took it home. It has a brass plug in the bottom with a 1/4-20 screw sticking out to screw into the multi-head cleaning rod you see it attached to. The spring is supposed to be soft soldered to the plug but I am not sure there is a really good joint there, although is has not come apart. But you could just fit a dowel inside the spring and make a worm with a dedicated handle.
For a 1.75" spring, consider garage door springs. They are tension springs so they would need to be raised to a red heat and stretched out some to spread the coils. They are way too long for just one worm but you might be able to find a broken one at a garage door shop and use it since there is no risk of the garage door falling on you if your worm breaks, which it wouldn't do anyway.