Do you have access to either Adobe Premiere Pro or After Effects as you can use either a mask to hide the parts of the face you don't want to see. Or you may be able to use an 8 or 16 point garbage matte and drag the points around the lips. You would put this on video track 2 and put a still image on video track 1, the duration of the still image would have to lengthened to cover the entire speech.

__________________
Better than a poke in the eye with a pointy stick any day...