Books are great places to find primary source material. Look in the appendices & exhibits in books on your topic to view excerpts of diaries, interviews, facsimiles and more.
Below are examples of book search queries that you can input into Library Search. Change your search query to reflect the specific drug trade you are researching:
(Drug traffic* OR Drug control) AND "United States"
"Opium Trade" AND (Asia or China or Japan)
Library Search also includes information about and links to a number of online government documents which can be primary sources.
Other keywords you can use to retrieve primary sources when combined with the name of your drug trade include: