Hi Mark, you need to order the CDs directly (it’s like the 2 must-have DVDs for the Cambridge Latin Course—at least when I got them, you needed to go directly to Cambridge).
The email addresses to contact still seem to be listed on the OUP page for the commentary in the “Description” section, so hopefully they still work (it was around a decade ago that I ordered):
A recording of the full text ofThe Agamemnon in Ancient Greek, for use in conjunction with the commentary, has been produced under the direction of David Raeburn. It is available on two CDs, together with explanatory notes, priced £9.99 plus postage from Blackwell’s Bookshop (> classics@blackwell.co.uk> ) and The Hellenic Bookservice (> monica@hellenicbookservice.com> ).
https://global.oup.com/ukhe/product/the-agamemnon-of-aeschylus-9780199595617?cc=gb&lang=en&
PS we had a discussion about these recordings here a while back:
http://discourse.textkit.com/t/rhythm-of-the-chorus-e-g-agamemnon/11262/1
Cheers, Chad