Scabbard of Many Blades (5000 gp) plus Quickdraw lets you sheathe one weapon and draw another, as a single swift action.
Blink Back Belt (5000 gp) automatically retrieves and sheathes your thrown weapons (but only thrown weapons).
Mixed Combat is another Path of War feat (also printed in Ultimate Psionics, and a class-feature of Bushi archetype), which lets you sheathe as a free action. It's not restricted to AOOs, unlike Improved Quick Draw.
Signature Skill / Rogue's Edge: Sleight of Hand with 15 skill ranks lets you draw or sheathe a hidden weapon as a swift action.
Phantom Sun Stance (Path of War, Solar Wind discipline) lets you draw a temporary copy of a thrown weapon, while leaving the original in your sheath. Unlike Blink Back Belt, you don't have to actually throw it; you could pick a dagger or spear or anything else that's usable both as thrown and melee.
Spiritbound item quirk might or might not work. A generous interpretation might have it teleport back to your sheath whenever you drop it, and/or just be in your sheath whenever you want to draw it. But RAW doesn't specify on the granularity of action economy.
-2 Cursed Sword might or might not work. It's unclear whether it literally teleports to your hand when you try to draw something else, in which case you can drop the sword as a free action and then "draw" it from the floor as easily as you could draw something from your belt; or whether it's merely a mental compulsion that never expands your options.