This SD card holder clips to display support, through the (parallelogram shaped) centre hole.
With slicing, I orientated the card slot holes to face up. Set the opposite face to touch the print bed (as shown in one of the pictures). Supports are required for the clips.
It's a snug fit but theres a little bit of give on the tongues to let you push it through then lock into place.
Edit: added new STL model which holds 6 regular sized SD cards.
The author hasn't provided the model origin yet.