Have you looked in the bibliographies of Robert Chazan's
<Medieval stereotypes and modern antisemitism>, Louis Feldman's <Jew and
Gentile in the ancient world : attitudes and interactions from Alexander
to Justinian> and, though its focus is for the most part host
desecration, Miri Rubin's <Gentile Tales>?
In addition, there is an early tale of Jewish persecution of non-Jewish
children refuted in Josephus' Contra Apionem, an apologetic work which
circulated less widely in medieval Europe than Josephus' historical (but
also apologetic) works. Your question also reminded me of something I've
meant to learn more about. (If memory serves) Isn't a young man (a
boy? a child?) crucified by Jews in Historia Tripartita, the translation of
three Greek historians (Sozomenus, etc.) associated with Cassiodorus?
Department of History
University of North Carolina, Chapel Hill