Man I haven't seen many 4 inch assisted openers but a pretty close run at 3 3/4 is the zero tolerance 0300 series. 0301 0302 0303. they are amazing blades with a killer warranty. big beefy things. titanium frame lock, s30v. great blades.
Im no expert on knives and I know that alot of the high end knife owners don't think much about Coldsteel knives but I bought a Rahah II it has an 8 inch handle and a 6 inch blade. You can even catch it on your pocket on the way out to open it.