This book, Alfred Korzybski: Collected Writings, 1920-1950, from 1990 is only available second-hand – too expensive. I then found the Google edition below.
This book and all of Korzybski’s books are for sale cheaply at General Semantics Institute online
I a Bought Science & Sanity from GSI – arrived in days! It is also online here.
Alfred Korzybski: Collected Writings, 1920-1950 follows (embedded)