Okay the title sounds ambiguous because I have yet to find a good way to phrase what I'm looking for.
What I want to accomplish is having a physical cable with an SD card shaped plug on one end, and something such as a USB plug on the other which I can hook into a device and feed SD format data through. I hope that makes sense.
The end goal involves a 3D printer. I have a 3D printer which only reads files from an SD card, but what I want to do is essentially hook up a Pi or such to that SD port and have the 3D printer read from a virtual drive on the Pi.