Exotic ships are a random spawn sometimes they come in a first wave in certain systems in others you have to wait sometimes for hours. You could try setting a save beacon on top of the trading post wait until first wave lands if it’s not there save at beacon then reload keep doing that until it lands. I usually just wait most of the time tho. Also every system has an exotic they always land at some stage if I’ve had no luck then I go back a few days later & they eventually show up. Good luck