I found the card holder box http://www.thingiverse.com/thing:30592 and liked it very much. To faciliate card retrieval I mirrowed the opening in the front and added a lid that can be fastened with a rubber band easily. Also I increased the height of the holder a bit and reduced the thickness of the base area.
agricolacards2lid_fixed.stl | 102.1KB | |
agricolacards2_fixed.stl | 163.5KB |