All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
That is an authentic Hadeeth, narrated by Ahmad and Abu Daawood, At-Tirmithi, An-Nasaa‘i and Ibn Maajah . It indicates that it is an act of Sunnah to apply Ithmid (antimony) to the eyes. Besides, it is an act of Sunnah for both men and women, and not limited to women as some might falsely think.
Antimony is a famous reddish-black stone that exists in the region of Hijaaz, and the best of it is brought from Isfahan (a province in the center of nowadays Iran), according to Al-Haafith Ibn Hajar .
We cannot tell you exactly where you could find it. But the people of Hijaaz are mostly interested in trading and using those things. For this reason, you could seek the aid of the reliable and experienced among them in that respect. Also, a Muslim should not be deceived simply by what is written on the product about the quality especially nowadays when cheating and deception have become increasingly widespread.