George Wald said the very similar “A physicist is the atom’s way of knowing about atoms” in a lecture he gave in the 1980s (apparently at several locations). George Wald: Life and Mind in the Universe
The first law of quotes is that they will be attributed to the most famous plausible person - and Sagan trumps Wald.
In this article from 2022 he credits Richard Feynman. He does indeed traffic in apocryphal quotes, it seems.
It’s funny that he gives credit elsewhere when it might be a Brian Cox original. There’s probably a term for an original phrase presented as a quote. Does anybody know that? I wonder who’s quote it’s going to be next time he’s promoting something.