There are only four literary texts that mention the Taurobolium. I’ve already posted translations of the relevant passage from the Peristephanon of Prudentius, and the anonymous carmen adversus paganos. The other mentions are in Firmicus Maternus and the the Augustan History, under Heliogabalus. A look in Clauss-Slaby’s database of inscriptions reveals a lot of people and altars that have undergone the rite too.
The Vita Heliogabali 7 online at Lacus Curtius gives this mention.
7. He also adopted the worship of the Great Mother and celebrated the rite of the taurobolium; and he carried off her image and the sacred objects which are kept hidden in a secret place. 2. He would toss his head to and fro among the castrated devotees of the goddess, and he infibulated himself, and did all that the eunuch-priests are wont to do;35 and the image of the goddess which he carried off he placed in the sanctuary of his god.