It's an iPad Sock! No, it's not a carbon copy of Apple's much-maligned but still available iPod Socks, but rather a larger, similar Belkin release called the Cap Sleeve for iPad ($40). Rather than selling a bunch of iPod Socks in different colors within the same package, Belkin's knit Cap Sleeve is sold one to a box in either black or purple with a second accent color, and obviously is large enough to hold the iPad bulging inside. It's the rare iPad…