You are required to have an interview for your speech, as it's important to get the first-hand point of view of experts in your field. It's crucial that the person being interviewed be an expert on your topic. You may conduct the interview yourself, or you may find a transcript or video of an interview online.
NPR and CNN can be good sources of interviews online. You may also Google your topic and the word interview. For instance, if you were researching factory farming, you might search for [factory farm interview].