Blinds Pull Chord Coupling Broken

The gearbox / coupling on the window blinds is cracked. It is difficult to replace the entire unit. So, this small spacer takes up clearance in broken coupling, allowing shaft to be more securely held.
No need to glue or fix the spacer, there is sufficient friction to hold it in place.
Just slide over the end of the shaft.
It may be easier to insert it into the coupling with it removed from shaft.

Video of before condition: https://youtu.be/BS9Fji1SPwE