Francis,
There are two books that I would recommend on Eastern saints. The first is "Golden Book of Eastern Saints" by Donald Attwater, which was first published in 1938. Since it came out in the 1930's, your best bet to find a copy is through the library of a Catholic seminary, college or university, or, if your interested in purchasing a copy, try one of the online used book websites.
Here is the list of Eastern Saints contained within the book:
St. Basil the Great
St. Gregory the Enlightener
St. Hilarion
St. Malchus
St. Pulcheria
St. Theodore the Studion
St. Athanasius the Athonite
St. John and St. Euththymios
St. Nelios the Younger
SS. Vladimir, Olga, Boris and Gleb, Antony, Theodosius
St. Sava
St. Josaphat
SS. Sharbel, Rafka al-Rayes, and Nematalla al-Hardini
Blessed Gomidas (Armenian Catholic martyr)
Blessed Gabra Michael (Ethiopian Catholic martyr)
plus:
The Venerable Mekhitar(founder of the Armenian Catholic order Mekhitarist fathers)
Matthew Gregory Nekkar (Syrian catholic martyr)
The second book, "The Saints of the East" is also by Donald Attwater, and is a 1963 revised version of the "Golden Book of Eastern Saints".
Both books I highly recommend are worth reading.
I hope this helps.
P.S. Saint Sergius of Radonezh, a post-schism Russian Orthodox saint, is listed in Butler's Lives of the Saints.