A Bar of Hair Covered Soap is harvestable from A Bar of Hairy Soap, dropped by one of the Devolved Squatters that you put in the drowned room when you were doing the quest, Devolved Recovery, for Antharo Quarum.
Get to it quick before it dissolves to get A Bar of Hair Covered Soap. You need 9 of them to give to Omi for Circuit Diagrams, the rare binder for a collectible book.
The soap is Bound to Account and max stack is 9. You must have all the pages of the book, Circuit Diagrams, before you can buy this binder.