You don't need to find an opinion article. Articles that contain evidence are even more useful for making an argument. Types of evidence that can help include:
Smoking Gun photograph ©Charles Knowles, used under a CC By 2.0 license
Some article databases have a lot of content about current events and debatable topics. (CQ Researcher is also a great source for choosing a topic.)
Find more articles in magazines, journals, and newspapers:
Find articles in reference books: