Thomas Jefferson "carried a small notebook made up of ivory leaves on which to record his observations. He would write down his measurements in pencil and in the evening transfer the data to seven large notebooks, each devoted to a different subject. He would then erase the ivory plates, readying them for another day of scientific inquiry." Source: https://www.artofmanliness.com/2010/09/13/the-pocket-noteboo...
This sounds very similar to what you're looking for: https://thenoteboard.com/. Sadly it doesn't seem to be available right now, but it's a pocket whiteboard made up of 3x5 segments. It folds down rather than being a stack of cards, but it may work for what you're thinking of.