I have been looking for this off and on for years. In my quest to watch all Hitchcock-directed movies and TV shows, I finally found a copy of this TV episode. It is from a show called Suspicion from 1960, an episode entitled "Four O'Clock."
It is now in Public Domain and available for download at the Internet Archive. They also have a few more of his films.
Now I just need to keep working on finding some of his really early and really rare stuff to watch.