Leighton Meester wears eyeglasses in her personal time, however, she has to wear contact lenses when she work. The favorite type of glasses she like to wear is black one with big frame as I can see. She has lots of personal photos can proof this.
There's nothing special for this kind of glasses, you can choose a similar pair for yourself. Whether online or offline can be convenient. My suggestion for you is to shop at real store, because you can try them on, then the final decision has to be right.
Well, she is one of the most promising actresses in America, and she has got a pair of good eyes, so she does not wear glasses, except for some particular needs, so sometimes we also could see her wear metal reading glasses for ladies, which could be seen at Walmart, actually, there are lots of metal reading glasses for females over there. You could find what you want, trust me.