Lol, from vintage sources.. There's tonnes of old footage and films on the internet, and a lot of it is public domain so you can do with it what you want.
Youtube and plain old Google are great for this..
I generally take them wildly out of context.. Like one of my recent tracks has a sample saying 'it gets dark', sounding all spooky but I actually cut it from an old coffee commercial.
Got some cool foley percussion-type sounds of it too. It's a fun way to sample, you get to hear and see some really surreal stuff and bring that inspiration/vibe along when you work with them.
Grabbing samples like these pre-made from a pack, because they sound cool really isn't the same though.. it'll always sound cheesy,
like you need the sample to say something that your track can't communicate... artistically, that's not very strong. Like if you don't watch old movies, why have a sample from them?
Especially if you don't even know what movie it's from.