Where can I get a stronghold card?

Excuse me, could you please clarify where exactly one might acquire a stronghold card? I've been searching for information on this particular product or service, but I'm having difficulty locating a definitive source. Is it available through a specific cryptocurrency exchange, a dedicated website, or perhaps a physical location? Additionally, are there any prerequisites or requirements that need to be met in order to obtain one? Your guidance would be greatly appreciated.