How to get Coco Lopez in Serbia?
this looks like a question about logistics and I really don't know about shipping things to Serbia, but since you mention you only need it for Piña Colada, I have good news: you can make your own cream of coconut!
Find a can of full fat coconut milk (this should be way easier to source than Coco Lopez), ideally not under 10% fat content. Add sugar (Darcy O'Neil, who popularised this recipe, says 375 grams) and a pinch of salt, heat to dissolve, and you're done.
Homemade cream of coconut will not last as long as Coco Lopez and needs to be refrigerated, but it's as good (or better), cheaper, and easier to come by