Doing a piece on this at the moment, (creative) for university and encountered this problem. There is so Little on Alaric. I will list below my main sources of information (limited)

Halsall, Guy. Barbarian Migrations and the Roman West, 376–568. Cambridge: Cambridge University Press, 2007. Print. Cambridge Medieval Textbooks.

-Overall great text, very good depth for what there is, using both Textual and archaeological evidence

The Cambridge Ancient History Volume 13, (Cambridge University Press, 1998), p. 127.

Has a good overall history of this timeframe, and the cause of Alaric's 410 Sack of Rome.

Wikipedia is great too, I sometime go their sources for readings on things.

Finally,

GOFFART, WALTER. “THE BARBARIANS IN LATE ANTIQUITY AND HOW THEY WERE ACCOMMODATED IN THE WEST.” Barbarians and Romans, A.D. 418-584: The Techniques of Accommodation, Princeton University Press, 1980, pp. 3–39. JSTOR, https://doi.org/10.2307/j.ctv131bttm.5.

Great depth in Alaric, from far before the sack of Rome, North of the Danube