I*m pretty sure they will only take the SD card supplied from Mazda. I*m pretty sure it*s Tom Tom navigation, plus it*s probably formatted specifically to be read by the Mazda software.
I believe the Nav card contains the graphics that drive the signs on the HUD (if your region has Traffic Sign Recognition System on the CX-5).
From the US Manual:
The TSR operates only if the navigation system SD card (Mazda genuine) is inserted in the SD card slot. Consult an Authorized Mazda Dealer for details.