From:
Twitter. By Carole Raddato, 2018. "Statue of a lion-headed figure associated with the cult of Mithras. On display in the Antiquarium di Villa Barberini (Castel Gandolfo), built on the remains of Domitian's Villa. It houses a collection of works of remarkable quality from the villa of the emperor."
From: Vermaseren, "Mithras: The Secret God", fig.29.
A couple of low-quality images are available from Arachne here, which gives the reference as "Castel Gandolfo, Italien, IT, Villa Barberini. Inv. no. 36419; Height: 67cm; Bibliography: P. Liverani, L'Antiquarium di Villa Barberini a Castel Gandolfo (1989) Cat. no. 36.".