You could probably adapt most skirt patterns. I think the key is to use a fuller skirt so you don't see any bulk underneath and also to make the short portion out of a stretchy thin fabric. Then it should just be a matter of stitching the shorts into the waistband as you would a liner.
I have done this. I just used cotton for both parts - the shorts and the skirt - and attached them to a waistband. The skirt has to be flared sufficiently right from the waist, so you don't have bulkiness there. You can also attach both parts to a yoke, which is very popular right now.