My Kershaw Outcast works pretty well as a neck knife for me. Ten inch D2 blade, 16 inches overall. Nicely concealable (by me). Takes a while to whip it out without hurting myself, though.
You only want one new one? That's easy. It's when there are several that you cannot live without at the same time that will getcha.
And for that Outcast kneck knife, if you want to sell It to fund the new knife let me know. I'll help u out. I want one of those so bad I cannot stand it.