Yes, it is fun to run an old newsreel once in a while, but where do you find them... good question?
I have a couple somewhere in my booth along with over a hundred cartoons and several reels full of of old daters.
The problem with newsreels is that they were throwaways. You got new ones two or three times a week and you threw them away. When the next one came they were considered worthless. As they were only several minutes long, it wasn't worth the shipping charge to return them. They didn't want them back anyway.
Whether the studios kept copies of them all, I have no idea. I guess it wouldn't hurt to ask.