"a charm of" is a correct and usable phrase in written English.
You would typically use it when referring to a group of birds, such as a "charm of finches."
In joyous contrast, the disarming illustrations and informative and witty words of Matt Sewell's A Charm of Goldfinches & Other Collective Nouns (Ebury) is utterly delightful.
It had a charm of its own.
This period of melancholy hiatus can have a charm of its own.
It's almost so ugly it has a charm of its own.
A single bookstore, but one considered a bellwether, even a charm of sorts for the industry.
She throws into the piece a charm of expression quite indescribable.
Early on, Osborne launched a charm offensive of cosy chats.
It has a certain charm, of course, the way a Panzer tank has charm, but all in all I think it's a deliberately offensive design.
That probably makes a special charm of "Cave of Forgotten Dreams".
Although not immediately beautiful, the city of Liège has a gritty charm of its own.
He combines the tenacity of a cockroach, the charm of a fox, and the tolerance of a half-dozen linebackers.
