From which source can you find Castoreum, a unique additive that was used in vanilla ice cream, puddings and syrups for decades?

Castoreum is derived from a beaver's castor gland near its anus. It is very aromatic and sweet smelling. They use it for mating and to mark their territory. It has been used for over 80 years to enhance the flavor of vanilla,strawberry and raspberry flavors in ice creams, syrups and puddings. The FDA (Food and Drug Administration) regards it as a safe nontoxic ingredient. It was used in ancient days in medicine primarily to treat headaches. It contains acetylsalicylic acid, which is the main ingredient in aspirin, making it a highly effective pain killer. It was also used in perfumes and in lamp oil. There is even Castoreum liquor made in Sweden. Nowadays, because the cost of extraction is so expensive, it is primarily used only in fragrances.