Look Pivot/FKS part problem

Hi all
I broke one and I lost another of the black plastic caps that sit on top of the connection between the metal arms and the dildo of the Pivot/FKS.
It seems that there's no replacement part so I thought to have it 3D printed.
The question is: how do I make it pop out without breaking it (2 are still intact)?

Thanks!

Which part precisely? Post photos.

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Yeah...that's one:

Attachment 294982