So here is pattern for making your own sunglasses case (pdf).
And here's a PDF of the instructions.
If you've sewn before, you might want to consider making a double sunglass case, great for keeping two pairs - I have my "it's kinda bright" pair and my "holy cow, I'm going blind" pair - or you could keep your iPod, money, and cards in the other slot. (That's the picture on the right)
Join me tomorrow for the double layer sunglass tutorial!