I have both of these cases for my OQO however I don't use either since I prefer no case at all. This is okay during winter months when you wear a coat. I know this will bite me in the a__ one day so am looking out for someting to come along however I not sure what will tickle my fancy.
Check out:
link
They acutally have a thin one and a thicker one. They are of good quality and fit my OQO pretty snug. The inside dimensions of the thin one is approx the same thickness of the OQO and fits very tight. The thicker one is approx 1/3 to 1/2 thicker outside and inside and will probably allow an extra battery to b carried.