In the Netherlands you can buy kemirienut paste at the toko or the Asian supermarket. If you can't find it, use 2 tablespoons of cashew nuts.
Trassi (or belacan) is fermented shrimp paste. The smell is disgusting, but it works like anchovies in some European dishes, you can't taste or smell the yuckiness after cooking the dish. If you can't find it (it should be available in Asian supermarkets), just leave it out.
If you can't find palm sugar (it should be available in Asian supermarkets), substitute with (dark) brown sugar.
If you can't find kecap manis (it should be available in Asian supermarkets), substitute with Chinese soy sauce (not Japanese!!) and a teaspoon palm sugar, brown sugar or treacle.