Unfortunately TD's aren't willing or able to source this part separately. I lost a spring and ball and no TD wanted any part of that action. You can buy substitutes for the springs and balls on Amazon but the click spring is a different matter.
I don't think you can even buy the gen part by itself. I've only seen the entire gen click spring set for sale.
What I think I would do immediately if it were my issue is buy a substitute spring and ball and use it there temporarily. That would keep the bezel evenly tight, and allow it to rotate albeit in both directions without a distinct click. Then I would see if any member has one they would offer up or has an old cheap dead watch with a working bezel and buy it for the click spring. Failing all that, I would attempt to fashion one myself by carefully sanding, filing or grinding down a correct diameter drill bit shank for example to a close approximation of the size and shape of the click spring. I'm confident one could be made that would work.