Unfortunately, the cassette itself, does not seem available on the market. I have a suspicion, this is the amazon reference. I am not sure.
For future reference, here are the details.
Caedmon cassette CDL 51249
Selections from the Bhagavad-Gita
The Song of God
Read by Zia Mohyeddin
Introduction read by Christopher Isherwood.
[from the rear flap]
Caedmon records, Inc., 505 Eithth Ave., N.Y., N.Y. 10018
[seems that the cassette was made in 1968 and costed $12.95]
[Some library stuff]
LC # PK3633.B5 P73 Music # TC 1249 Caedmon
A couple of web searches on Caedmon and Bhagavad-Gita reveals that most of this information is authentic.
The google search leads to the following link from NYtimes:
(article titled: FROM 'GENESIS' TO 'JESUS CHRIST SUPERSTAR' from May 10, 1981)
There is, though, a hypnotically compelling reading of selections from the Bhagavad-Gita on Caedmon (TC 1249, cassette CDL 51249) by Zia Moheyddin. The translation, in poetry and prose, is the celebrated one by Christopher Isherwood and Swami Prabhavananda. Isherwood himself provided a thoughtful introduction to this reading, which can be followed with the aid of the New American Library paperback of the whole book. On this remarkable recording, as Krishna explains to Arjuna why all action should be performed in a spirit of non-attachment -in Isherwood's words, 'without desire and without fear'' - the very purpose of life in Hindu terms becomes luminously clear.