Where can I buy this light?

For what it's worth, that is a semi-flush light, not a pendant light. A pendant light is more or less free to swing around on a chain, a cable, or a long tube. A semi-flush light hands down a short distance on some sort of a more or less rigid support. A flush mount light has the body of the fixture directly attached to the ceiling surface but is not recessed into it.

I realize that the distinction may seem a little pedantic (or even pendantic, if you like puns), but understanding the differences may well be helpful when attempting to look such things up in the future.