Spring for dividers?

[Deadeye]

I have a nice pair of old dividers from my late father in law. The spring/clip at the top that holds the two arms in tension (outwards) is broken.
Rather than ditch them I'd like to replace it if possible. Any ideas where to start?
The broken piece I have suggests about an inch in diameter, springy metal, and about 80% of a full circle.

 

[AJB Temple]

You can buy, say, Faithful spring dividers from Amazon for £3.15. Cannibalise the spring. You are unlikely to find spring steel on its own.