Crown tap size conversion?

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I have a watch with a .9mm winder stem but a screw crown and tube with 1.2mm thread. Is there a converter like a stem extender which can make a 1.2 crown fit a .9 stem?

Before anyone comments, I have tried to get 1.2 winder stem but cannot source one! Any advice much appreciated.
 
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Available from Esslinger, and most other watch material suppliers. These are slot in packages by size, of 10 or 12. So don’t try to buy just one.