Kershaw Leek
I guess for me, I'd like a 3" blade that handles like a pairing knife or an Opinel, but I'd like it to open with one hand.
That sounds like a description of the Kershaw Leek.
Most of mine have metal handles and are frame lock, although I do have one or two that are black FRN (nylon) plastic handled with liner lock.
Three-inch blade, assisted open, light and thin blade, and narrow enough to do vegetables and fruit.
Oh, and seriously pointy. That long, tapered point gives you a good inch and a half of reasonably narrow blade for those little fiddly jobs.
All of mine are "shavin' sharp" from the box, and required no touch-up to be immeditately useful.
If you wear slacks, get the one with the metal handle. The smooth surface won't tear up the fabric of your trousers when you use the pocket clip.
The knife is light enough that you
could remove the clip and just drop it in your pocket.
Right now I'm carrying a Kershaw
Pack Rat (Sandvik steel, orange G10 handles) in my pocket. It also has a three-inch blade. I have removed the pocket clip. It's thin enough and light enough that it's no bother having it ride down in the pocket.
(A larger picture of
this knife in orange can be seen here.)
It is also assisted open, although not quite as smooth and quick as the Leek.
The blade is heavier and a little thicker than the Leek's blade, and is not nearly as pointy or tapered. It's a good general-use knife and I find it comfortable in the kitchen, but using it to cut up apples requires a slightly different method than I would use with the Leek.
From your description, I would suggest the Leek would probably be closer to meeting your requirements.