Currently White Pearl is only obtained as a Fishing Rare.
According to this site it should also be a rare drop on SA Renowned and from Axem the Curator (likely Bulging Museum Bag since delicate scales are there too)
https://uo.stratics.com/database/view.php?db_content=gameitem&id=2181
Also, some guy on the forums mentions that you can obtain them from "SA quests* (assuming Axem)
https://stratics.com/threads/white-pearl.169253/
According to this site it should also be a rare drop on SA Renowned and from Axem the Curator (likely Bulging Museum Bag since delicate scales are there too)
https://uo.stratics.com/database/view.php?db_content=gameitem&id=2181
Also, some guy on the forums mentions that you can obtain them from "SA quests* (assuming Axem)
https://stratics.com/threads/white-pearl.169253/