Do not buy a Serpa holster...
For IWB and OWB in the same holster, I'd get a Raven Phantom or clone. All the suggestions have been for only IWB or OWB, so in that case, I'd go with High Noon for all your leather needs.
You also don't have to be carrying openly to use an OWB holster. The above mentioned Phantom conceals extremely well OWB.