I am a fan of Oberon cases (sleeves). Pricey, but excellent craftsmanship. I think a leather case for the iPhone is somewhere around 40 dollars. My phone has been very well protected and the sleeves are beautiful to boot.
I don't believe they have an exact iPhone 5 case on their website yet, but I own one for the iPhone 4. I received my new iPhone5 on Tuesday and the new phone still fits, even though it is a bit taller.