Happened upon a great find! Coincidentally while I was on a local search for the Vince jacket at a few "last chance" stores I know to carry that brand, I happened upon this field jacket by Projek Raw. As you can see, it's the closest match to the Vince I've seen yet (and trust me, I've looked at just about every variation of field jacket there is online).
It does have its slight differences. I'm going to have a tailor add gold snap buttons to the pockets and replace the silver ones down the opening with the same. Also, remove the small epaulets on the shoulders.
But if you notice it has the same details across the back with the hem, same pocket shapes (though the bottom two don't have outer seams like I think the Vince does), same collar with zip-out hood and is the same brushed twill material. The color is also really close.
Sure, it's not a legit Vince and doesn't satisfy the quest for the real deal of course but it at least tides me over until I find one. Just thought I'd share! Happy hunting.