I have seen such glasses from Amazon which is a good place for you to buy things. You could go to that place to have a look. The price there is suitable and the quality is good. You may spend some time on choosing the suitable and perfect one there.
I just checked. From of the image of wiz khalifa, we can see that the black glasses he worn is very common. And It seems like a wayfarer style. I can find such black eyeglasses frames at almost every eyeglasses shop. I have seen such black eyeglasses frames at Firmoo.com. You can search "black glasses" from their sites. Besides, Other eyeglasses shop such as Walmart also provide such black eyeglasses. You ca have a try.