Versions of these statues actually made their first appearance in 2002's Star Wars: Attack of the Clones, in a pretty significant place: the office of Palpatine (Ian McDiarmid), when he was still acting as Supreme Chancellor of the Republic (and hiding his true identity as Darth Sidious, the Dark Lord of the Sith). They can be seen during the scene when Palpatine meets with Anakin Skywalker (Hayden Chistensen), as the two are having a little walk-and-talk.
The conversation is incredibly significant, as Palpatine tells his future apprentice that — in direct contradiction to the opinion of Obi-Wan Kenobi — Anakin doesn't need guidance from anyone. "In time, you will learn to trust your feelings," Palpatine says. "Then, you will be invincible." As this dialogue is taking place, a statue of Sistros can be seen in the background.
In the 2014 novel Tarkin, a canon work taking place shortly after the events of Star Wars: Revenge of the Sith, it was revealed that after Palpatine became Emperor, he converted the remains of the Jedi Temple into the new Imperial Palace. He took up residence in the palace, bringing the Sistros statue with him. Obviously, old Palps felt a pretty strong connection to Sistros in particular, and the Four Sages in general — and he wasn't the only one.
Mas Amedda, a former Republic Senator featured in the Star Wars prequel films who defected to the Empire during the Clone Wars, was seen to have a small statue of Sistros atop his staff. Also, Supreme Leader Snoke — who was revealed in Rise of Skywalker to be a clone, and a puppet of the Emperor — wore a ring inscribed with glyphs of all four Sages.
