Mainspring

4.7mm wide, ~~245mm long, with a ‘T’ end. The narrow part of the opening for the mainspring ‘T’ is 2.65mm and the wide part is over 5mm. Thickness is 0.18mm. Perhaps if you can’t find the exact end, I can grind down a spring with no end on it or convert some simple end to work.

Mainspring barrel: