If you do have a spare I may be interested because for the life in me I can't get the maps to update using a standard SD card. I'm still on the maps that came out of the factory.
It's only nav pro that uses any SD card. As Talk-torque said you can only use the VW SD card to update Discover nav. Do you have nav pro?
In that case then you won't have a VW supplied card and can use a minimum 32gb card. Maps are easy to update, what exactly are you having a problem with?