As my status guide shows, the vast majority of the 72 episodes of ABC’s The Mike Wallace Interview are collected (and have been digitized) at the Harry Ransom Center at the University of Texas. Several of those episodes exist solely on audio. However, one of the most controversial episodes–in which Wallace interviewed Mickey Cohen–is not part of the Ransom collection Nor can it be found at any of the other big four television archives.
(You can read about the controversy in my article about the series).
It can, however, be found at Archival Television Audio, Inc. Phil Gries contacted me earlier this month to let me know that ATA has the complete Mickey Cohen episode (originally broadcast May 19th, 1957). It also has the retraction read by ABC’s Oliver Treyz the following week; Ransom has the episode (with Senator Wayne Morse) but the retraction by Treyz is not included nor is a brief retraction by Wallace himself. I’ve updated my status guide to reflect this.