I have a PS Vita, and here's what I'm using to protect it. Yes, it's a clean white sock. Turned inside-out, of course, to keep away lint. Low-cut, I might add, to eliminate unneeded tube-sock. I'm a size 11.
Here's the rub with high-end electronics bearing tremendous screens: we're terrified of scratching them, and yet so few come with cases in the box. Like any recently released device, few peripherals are available from the get-go. I remember hunting for an iPhone case when the first one was released...same with the iPad.
The original PSP did come with a soft little neoprene sheath, but I lost that slipcase long ago. However, the Vita is wide enough and long enough to fit in a sock just fine--word to the case-thrifty. Of course, you can always buy one of Sony's first-party cases for as little as $19.99, or even try fitting an old PSP case on for size, but where's the fun in that? After all, haven't you ever given your gadget the sock treatment?