What is the offical Sony PS2 memory card? I want to get one but I don't know which one is the offical one. I've seen all these different ones in all these different stores but I don't know which one is the offical one? I saw some yellow card at Wal-Mart that the clerk said was an offical Sony one but from what I remember it said Nyko on it not Sony?

Any help or pictures would be great. Thanks.