I will offer a word of warning regarding buying memory cards off eBay, especially SanDisk. There are many more fraudulent SanDisk cards on eBay than there are legitimate ones, and you aren't saving a great deal of money to justify the risk of getting scammed.
That said, any SanDisk Micro SD will work. The only limitation will be the memory card size (4gb, 8gb, 16gb, etc.) and I'm not familiar what the max is for the Storm 2, but certainly 8gb will work fine. I would suggest simply going to a local store and buying one, or at least buying one online from a reputable retailer.
Semper Fi 3/2/2
"Wow" is now overused. Therefore, I will use "Magic bananas" instead.