Its structure is Chapter-Introduction, Gita Chapter. If I remember correctly, the authenticated background information is mostly what goes on in the introduction to each chapter (i.e. 'Drona was born a brahmin, a member of the priestly caste, but in search of wealth he took up the way of the warrior and excelled in the knowledge of arms,' since the background of the character is not explained in the Gita itself).
I don't remember much personal commentary in the chapter introductions, and you can easily skip them and just read the Gita translation itself, since there are no commentaries interspersed with Gita translation.
I'm not sure if that meets your 'no personal commentaries' criteria, but I liked the translation. [Edit to add: listing some of the translations you have found wanting might help guide suggestions.]