Originally Posted by rhm

I just realized: the place you are most likely to find one of these is on an old saddle. So again looking at eBay, I found a couple, such as this:

Vintage Black Mesinger Bike Saddle Cruiser Bicycle Seat-Coil Springs | eBay

That's clearly some piece of junk saddle with a Mesinger cover over it. It's overpriced by $20 or so, so I'm not recommending it, but maybe it'll give you an idea what to be looking for.