There's a bunch of cases on eBay, lots of colors and designs. You see some of the same ones in the mall kiosks, but for much more money. I picked one up for under $7 with shipping. It's hard plastic, with that coating that gives it a rubberized feel. It fits fine, and there's no problem with sliding the keyboard. There's some fancier cases for just a little more.
Search eBay for Optimus Slider case, Enlighten case, VM701 case, LS700 case, or VS700.