This is not a video,  but a still photo that shows while an 22 minute audio plays,  but a complete speech King gave that contains most of what he said at Riverside (I assume it is a different speech because of his references to “today” instead of “tonight”,  and it doesn’t exactly match the transcript of Riverside—some things are out of order,  but most phrasing is intact).  Awesome speech (surprise surprise)

Source: YouTube – Martin Luther King, “Why I Am Opposed to the War in Vietnam”