@HardWithStyle I played RSE on a little bit older version 1.3 and here is my quest log for red sands island different then yours. I dont know what changed in new update something in translation or quest itself but you got some bug/error in your version
After fighting Zigurd quest goes : talk to shopkeeper in Elon, go to Reha in castle talk, then Nameless castle and after talking to Dark Mistikus he give you map to Red sands island and that was it for me. I dont know any other way to get map for new island, because that`s how quest is made. In your screen i see that order in which you visited islands is different then in my quest, if you have some save after fighting with Zigurd try going in my order Elon-Reha-Nameless and see if you get map for red sands. Good luck.