I need to look in Quasten for some references. In the mean time I found this online at CCEL:
A number of his fragments have been edited by Carl de Boor (ZKG, vi. 478-494; TU, v. 165-184), and his history seems also to have influenced the “Religious Conference at the Sassanid Court ” (ed. Eduard Bratke, in TU, xix., part 3, 1899). A few other fragments of Philip’s writings are known to exist, and it is possible that he was also the author of the still unedited De tinctura aeris Persici et de tinctura aeris Indici.
At least some of the the ZKG and TU ought to be online. I wonder what the last text is?
There is also material which was published by Dodwell, on the catechical school at Alexandria, as Lardner mentions here:
…there is a particular account given of him [Athenagoras] by Philip Sidetes (who flourished in the beginning of the fifth century,) in a fragment of his Christian History published by (e) Dodwell. Philip says, Athenagoras was at first a Heathen, and that he intended to write against the Christians : but when he was reading the scriptures, with a view of making his work the more complete, he was converted. He says, that Athenagoras flourished under Adrian and Antoninus the Pious, to whom his Apology was presented; and that he was the first president of the catechetical school of Alexandria, and master of Clement, who wrote the Stromata.
e. Append. ad Diss. Iren. p. 488
I am pretty sure I obtained a copy of this long ago, and it is longer than this excerpt. Another version of the same is here:
The statements of Philip Sidetes are as follows : “Athenagoras was the first leader of the school at Alexandria, flourishing in the time of Adrian and Antoninus, to whom he also addressed his Apology for the Christians. He was a man who christianized in the cloak and was president of the academic school. He, before Celsus, having been eager to write against the Christians, studied the Divine Scriptures in order to contend more carefully, and was thus caught by the all-holy Spirit; so that, like the great Paul, he became a teacher instead of a persecutor of the faith which he persecuted. Philip says that Clemens the writer of the Stromata was his disciple, and Pantsenus was the disciple of Clemens.” This fragment was first published by Dodwell in an appendix to his Dissertations on Irenseus.
There is an interesting discussion of the manuscript which contains these fragments, the Barocci 142 in the Bodleian in Oxford here. Apparently C. de Boor borrowed the ms. from the Bodleian in the 19th century and took it to Germany. Those were the days! De Boor published notes on the ms. in ZKG 6 (1884) 478-94.
UPDATE: It turns out that I have the ZKG 6 article in PDF. I also have the H. Dodwell, Dissertationes in Irenaeum. Accedit fragmentum Philippi Sideti hactenus inediti de catechistarum Alexandrinorum successione. Oxford, 1689.
Quasten lists as well: C. De Boor, Neue Fragmente des Papias, Hegesippus und Pierus in bisher unbekannten Exzerpten aus der Kirchengeschichte des Philippus Sidetes (TU 5, 2), Leipzig, 1888, 165-184. A. Wirth, Aus orientalischen Chroniken, Frankfurt am Main, 1894, 208-210 (on Adam and Eve). E. Bratke, Das sogennante Religionsgesprach am Hof der Sassaniden (TU 19, 3) Leipzig 1899, 153-164.
I wonder if there has been any additions since the 1950’s.
TU 5 is here, and de Boor is on p.322-341 of the PDF. Apparently “TU 19” is “TU 4 (New series)”, and is here. Bratke starts on p.448 of the PDF. Something about Philip appears in the text he prints, on p.476 of the PDF. Wirth is here, on p.208 of the PDF.