Script City is the company to go to for the original scripts of hundreds of movies, TV movies, TV episodes, as well as books about how to write scripts, how to sell scripts, and the movie biz in general.
I bought a copy of the script for my favorite movie, Red Dawn, from them. Looking through the script, I almost had a spasm. The original script held together a lot better and told a far more coherent story than the final product. If nothing else, I reappraised John Milius, the director, pretty thoroughly.
If you want to write a movie script on a subject that has had several movies made about it already, procuring copies of the scripts of these movies might save your brainchild from being