My basic SD card holder printed nicely. It only holds the cards loosely, but that is good enough for my needs. I figured I could put this holder into an envelope or something like that to keep the cards from falling out, but it turns out that it just fits into a paper clip box. 🙂 
The only issue with its printing was that it stuck to the build plate. A flat-ended staple remover helped me pop it off the plate.
Another new step today was to use an SD card reader with a USB connection. That worked on my office computer with no problems.