But where do you source the files? I'm willing to pay for a deck, but it seems impossible to find good information without spending a ton of time researching it. Too much noise/signal ratio in this space.

You're correct this is a problem. I paid for sprachenlernen24.de which is German to many languages and very good. Not sure about other source languages though.

Take a read on this: https://augmentingcognition.com/ltm.html

The author, among other topics, makes a case for the creation of personalized decks. That practice has been really valuable to me.

Yeah but I'm not sure if that's the way to go for learning your first 1000 words of a language, especially if you're just trying to spend your 15 minute commute doing something useful.