Stefan / Martin,
I just replaced a few of those springs and rubber blocks. You can ask any Antal dealer to order them from Antal. That is what I did.
Be very explicit about what you need using tracksize, pictures and other descriptions to make sure you get what you need.
These rubber block come in may different sizes depending on the car/stopper configuration. They just glue in place.
Also make sure the bolt that holds the "wheel" is tight. I lost one during a passage and apparently that happens to others as well. I use threadlocker to prevent the nut from loosening.