"commentator of" is correct and usable in written English.
For example, you could use it in a sentence such as "He is a renowned commentator of international politics."
My favorite comment was one accusing another commentator of being "a trembling dogsbody who's scared to death to breathe in front of the boss".
Will Hutton was business ethics commentator of the year at the Comment Awards 2014.
Not bad for a former color commentator of the Shreveport Steamer of the World Football League.
When an old-school commentator of Tyler's class cries wolf, you know something major is happening.
To nick the catchphrase of the greatest television commentator of the day: one nil!
He was also, effortlessly and by some distance, the coolest commentator of his generation.
In the past decade, she has become the most prominent female conservative commentator of her generation.
His younger brother Sayana, the minister of four successive Vijayanagar kings, is famous as the commentator of the Vedas.
John Rentoul, senior political commentator of the IoS, is author of Tony Blair: Prime Minister (Little, Brown).
He said his proudest moment was being voted sports commentator of the year in 2002 by his fellow sports commentators.
In his commentary included in the report the Australian's media commentator of many years Mark Day mentioned the finding.
