There is a whole genre of youtube videos with AI generated Feynmann voice based on those lectures. They are of surprisingly high quality.
I presume the original videos of Feynman are lost, or never existed?
I found this channel to be ok-ish.
The Feynman Lectures website does have links to recordings of almost every lecture, but no video. BUT there are thousands of photos --- many photos of each lecture, showing Feynman's blackboards.
Also, there are videos there of a series of 7 lectures at Cornell in 1964.