Question about where to get Upholstery spring

[Freddo]

Can anyone tell me where I might locate an upholstery spring for my 1967 Chev-c10 bench seat?
I ordered an upholstery cover for it and have taken off the old (I'm thinking original) cover and saw that one of my springs is broken. I included some pictures to show where it was located, as well as a picture of the spring. I'm thinking that part of the spring is missing. (maybe one square 'loop'...Hope that makes sense.)
It's under the left edge of the drivers side seat and probably gets compressed every time you get in or out, so it makes sense that it was the first to give out.

I'm guessing an upholstery shop might have 'generic' springs like this that could be cut down, but thought someone might know of a 'go to' place to get the exact piece.

All help appreciated!