They're called a "rod bracket" which I'm not sure how to translate into Croatian well. Also called "drop-in flange" sometimes. Here's an example, if you need a photo to show to the person working at your hardware store.
Worst case, HR auction sites will have them, like so: http://www.njuskalo.hr/zavjese/zavje...oglas-18671722 (#2 and #4 are what are being used here).