In general, you can use any commercially available SD card.

It should be formatted FAT32 or exFAT, which is standard when you buy a card. Special certifications (high speed cards – SDXC) for increased speed are not necessary and are more likely leading to misbehavior. A simple inexpensive SDHC card is usually quite sufficient.

However, we do not recommend using an SD card for storage purposes. The USB interface is much better suited, as it is more reliable and faster.  An SD card is only needed when restoring the factory settings (full init). In this case, an SD card and a USB device are required.

Since we have not tested all SD cards and the market is quite large, it is difficult to give a comprehensive recommendation.