2011 Merc Music Card reader

[CraigT007]

A friend has recently taken possession of a 2011 C63 and it has a credit card sized MP3 player card. I got him a flash card to SD convertor, as I thought it was the same as my Becker traffic master, but it's too thick to fit into the slot within the merc provided card slot.

Anyone now what type of adaptor he needs to let this read an SD card?

thanks