I actually had to order it online! (I read that they love to chew and destroy it and I wanted to see if they really do)
All the stores around here said they can't order any cork material for some reason. I guess because it goes from nature directly to sale and it might be "alive".
After I got the "stump" I made sure to put it in the ofen for a while and I am keeping te leftover stump in the basement.
So far I tried a swing = the round thing which I hung up, but aside from having chewed a "hole" in the circle they don't seem interested. (might cut that one up as well sometime)
And a sitting opportunity which you can see on the side of the 2nd last pic, Ludwig is sitting on it, for that I just cut a piece off and tied it to the side of the cage :3