Primary sources are documents from the time of an event. Examples are letters, speeches, photos, and newspaper articles.
The following book, located on the 3rd floor of the library, call number F869.L89 M447 2013, has a primary sources section.
The Zoot Suit Riots / Kevin Hillstrom
I did the following search on Google: zoot suit site:.edu
Adding site:.edu to the search limits results to educational sites. The Zoot Suit Discovery Guide from Pomona College has several useful things listed under Letters and Newspaper Articles. Use the navigation links on the right of the guide to find them.
By searching the Gale Virtual Reference Library database, I also found the Warren Committee's report on the riots from 1943.
Hope these help!