There is a prosopography of KL Kommandants that you perhaps already know about by Tom Segev, The Soldiers of Evil in which he held extensive interviews with several surviving SS Kommandanten. Segev is interested as a psychologist/psychiatrist.
There are the famous autobiographical (gallows autobiographies) of Rudolf Höß and Perry Broad, both administrators of Auschwitz. Likewise of Hans Frank (although not a KZ functionary certainly a perpetrator).
You might try the "Green Series," the War Crimes Trials at Nuremberg in which Otto Ohlendorf, a leader of the Einsatzkommandos, was tried and gave extensive testimony. Of course he expressed little remorse.
Try writing to the Institut für Zeitgeschichte in Munich where they must have extensive collections of post-war interrogations.
Mike Allen, Cleveland