The Fall of Civilization series: The Songhai Empire - Africa's Age of Gold https://www.youtube.com/watch?v=GfUT6LhBBYs

Paul MM Cooper's podcasts and video essays on YT are excellent. There's info on Mansa Musa in this episode: https://www.youtube.com/watch?v=GfUT6LhBBYs

Not of Timbuktu specifically. There are books on the history of West Africa, or Mansa Musa.