Thank you for allowing me to assist with your question.
Re: Lennon - according to Historian Jon Wiener, who spent 14 years working to gain access to the FBI's secret files on John Lennon and subsequently produced documentaries and wrote a book about the government's survielence of Lennon, the FBI's logs (obtained through the Wiener's use of the Freedom of INformation Act) there were no "bug" logs to show that Lennon was recorded on video or audio, or that his phone was tapped. If it happened - there's no official record of it.
Re: Malcom X - the same is true here, there are no records of audio recordings being made however, HE recorded conversations with THEM (FBI agents) While it is widely accepted that his phone and residence were wire tapped, we know they "listened" but there are no records indicating that those conversations were recorded and retained.
The FBI investigave records regarding Rev. Dr. Martin Luther King, Jr. have been ordered sealed until January 2027. This is according to the National Archive of records, Records of the Federal Bureua of Investigation ( http://www.archives.gov/research/guide-fed-records/groups/065.html
In general, when searching for information already made public, you can go the FBI "Vault" http://vault.fbi.gov/
and search or browse by name (you'll see names like Maryln Monroe and Gerry Garcia there as well). Or, the link above.
If I can be of further assistance, please let me know. I know this does not give you the direct access to the exact content that you identified, but I hope this keeps you from wasting time looking for media that does not exist.
I hope that alone is helpful to you. Please reply back if you have additional questions or concerns. If you have no additional questions please remember to rate my service before exiting the site so I can be credited for my time.