The second reference is almost correct, at least in the 1921 version of Prejudices: Second Series (available from https://archive.org/stream/prejudices030184mbp#page/n163/mode/2up) the quote is “…there is always a well-known solution to every human problem neat, plausible, and wrong.” (rather than “There is always an easy solution to every human problem — neat, plausible, and wrong.”)