spindown: How about your university library?
Tantrix: Tried it, nothing. Even interlending wasn't avaiable.
HypersomniacLive: What exactly do you need regarding Old Greek literature?
Can't promise you that I can be of real help, but won't hurt to look into it.
Tantrix: Not sure if you can get into it, but there should be ancient Greek hymns dedicated to the Egyptian goddess Isis since her cult spread in late ancient periods to Greece and Rome.
Just wondering if there is actually primary literature to those kind of hymns.
http://lotuspharia.freeyellow.com/thecircleofisis/id341.html I don't trust that source. so I wanted to look for primary Greek literature.
The cult (or mysteries) of Isis and Serapis (ape god, sometimes substituted with Osiris) heavily influenced early Gnosticism which, in turn, had some influence on early Christanity. Try a religion professor and your local university, who ever teaches the Gnostic subjects (Gospel of John, etc.) should be able to point you in the correct direction.