I wanted an SD Card holder for the Replicator, but one that could hold multiple cards in a relatively small space. I downloaded and printed one which promptly broke (the gap was just a bit too small to slide over the edge). There are many many card holders on Thingiverse, but I opted to learn how to design and print my own. So this is more of an design educational tool for myself. But it works too.
The cards are a little snug, so you may want to widen the gaps by about .5 mm, or just sand them down a little.
Designed in FreeCAD, and the file is included below.
Print and use.