I see no hint of an audio recording having been made, much less surviving & digitized, in the original article's description: https://www.cambridge.org/core/journals/journal-of-the-histo... It's too detailed to be retroactive notes by Simon or Borges, so I would guess Borges's secretary or a student simply transcribed it as they went.

This seems to be the version published in an Argentinian magazine:

https://borgestodoelanio.blogspot.com/2017/05/jorge-luis-bor...