I'm using a cheap Micro-SD card I bought from Tesco. It's a SanDisk Ultra 64GB, see the enclosed photo for details*. Ignore the scratches on the left hand side of the card, that's from just now, when I had to use a nail file to force the Micro-SD card out of the full size SD card adapter (that came with the micro-SD card), so I could photograph it . And forgive the not great photo quality, my mobile phone is old, and the photo was at maximum zoom, in not brilliant lighting.
The micro-SD card works fine with the Everdrive 64, and doesn't object if I delete or add new roms.
* I can't upload the photo to a website at the moment, so I've enclosed it here as an attachment,