The Sarmatians didn't have a hat with flaps worn over the face, but someone had a hat with flaps sewn above the face.
If you go to the Hermitage Museum's collections database and type in "Sarmatian", one of the entries that comes up is this:
You may notice that the caption says nothing about Sarmatians, but instead mentions the Tashtyk culture. The Tashtyks might be the same people as the Yenisei Kirghiz ( Name culture=lingo for archeological finds of uncertain affinity), but they're too far east to be Sarmatians (they definitely aren't Alans in service to Mongols). The child's coat from the kurta post is another Tashtyk artifact, but so close to Sarmatian style that I have no issue presenting it as something to base a pattern on for Sarmatian personae (steppe nomads shared a lot of similarities). This hat I haven't seen anywhere else so it's probably something particular to the Tashtyk.
Grousset, R., 1970, The Empire of the Steppes: A History of Central Asia, Rutgers University Press, 718 pp.
Xipoliya Yanke Suo Jian Xiajiesi Monijiao" ("Siberan Rock Arts and Xiajiesi's Manicheism") 1998 Gansu Mingzu Yanjiu