For 3 1/2", any small Kit Carson knife
For 3", small Sebenza.
However, the small Carson M16 with 3 1/2" blade and titanium is so light, there's no need to be carrying anything smaller. Why give up 1/2" of blade for no reason? I also think tip down carry is preferable for IWB, as I've had Sebenza's come open a little bit due to your body rubbing on it. With tip down, it's no problem.