Outer Limits episodes are available on video and on DVD from Amazon.com
The Outer Limits, episode #2
"The Hundred Days of the Dragon"
To create an impostor for the U.S. president, an Asian uses a serum that alters human form. Then, the President of the United States is murdered and replaced with a perfect double who intends to take over the country and then the world. The dead president's daughter begins to question her "father" and attempts to unmask the imposter before he accomplishes his master plan. Story is sort of a sci-fi version of the 1962 thriller The Manchurian Candidate