I had problem with original 3D printed servo arm slipping from the servo, that's why I made this adapter for the aluminium servo arm.
You will need aluminium servo arm 25T, see attached image.
Supports are already built in, don't forget to remove them.
For Czech guys: arm could be ordered from here, for example: https://www.bighobby.cz/alu--hlinikova--servo-paka-1b-25t--zlata-31mm/
The author marked this model as their own original creation.