I've broken the thumb tabs on my Schuberth E1 sun peak twice. Schuberth does not sell this part, so you have to purchase a new sun peak to fix the issue, which costs about $100. I decided to model the lock ring in FreeCAD, and it works perfectly. I modeled the left side and printed a mirror image for the right. I printed in both PLA+ and ABS. You will need to add supports also. Be sure to remove all remnants of the support before installing the new rings. Also, be careful when removing the old lock ring. You will need to remove a retaining ring that holds the lock ring in place.