I live in the Netherlands and don't know what to buy as an alternative for a doll carrier, needs to be sturdy but soft

Fusible fleece is an interfacing that has a fusible on one side (like a regular single sided interfacing) and a fleece like fabric on the other side. The fleece side is like a thin polyester batting. You could use a thinner poly batting with some wonder under (the two sided fusible interfacing - where you put it in the middle of two things and it fuses them together with an iron) if you can't find fusible fleece. I know Pellon makes fusible fleece but not sure if it is in your country.