I'm working on a build that uses the feats Great Throw and Knock-Down, so even with the errata'd version of Knock-Down I can still deal unarmed strike damage again with almost every attack. Problem is, I want to use a reach weapon for the initial attack (one that can't be used to trip), so I need a way to extend the reach of my unarmed strikes without extending the reach of that weapon, so there's an overlap.
Why can't I just use a different weapon, or no weapon at all? Well, I'm trying to pull this off with Eldritch Glaive (which attacks as a reach weapon), and I assume any trip attacks (which have to be made unarmed since the glaive can't trip) have to actually be within unarmed reach.
Is there anything that extends the reach of unarmed strikes without extending the reach of reach weapons?