https://www.youtube.com/watch?v=Q7N8vqyO7pc

This one is a little long (26 minutes) and might not work for you, but I would like to see even more short films riffed (another one I just watched that is telephone related that I liked was Dialing Tips - https://www.youtube.com/watch?v=z8M9_tCbW4Y), and YouTube has a wealth of great ones. The above came from Ella's Archives at:

https://www.youtube.com/user/Ella73TV2/videos

There is also:

https://www.youtube.com/user/shaggylocks
https://www.youtube.com/user/OldTVTime/videos
https://www.youtube.com/user/keyanage/videos

I love the fact that these shorts are easily digestible and cheap. I own most of the ones currently for sale from RiffTrax and watch them over and over, I'd love something new to watch.