mainspring for Slava stopwatch

[matabog]

Hello!

I measured the old spring in the Slava stopwatch that I opened here: 

The numbers are: 480-520mm/2.74mm/0.39mm, give or take a couple of microns

I couldn't find this combination on Cousins. Does anyone know where I could find one?

The ends are like this:

Thank you,

Bogdan

 

[oldhippy]

What is the cal of the movement?

[matabog]

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&Slava_5498

Slava 5498

[JohnR725]

I was looking at the sources I have as it look like an American pocket watch spring at least for the end. I can find some that are close at 2.7 mm and the length is about right but the thickness is a definite problem. The thickest spring I'm finding is .21 mm

[matabog]