I was going to say the Montbell Chameece. I have one in Large and it weighs 153g (5.4oz). I hope it comes back up in the US for you guys. I really like it because it is so light, but also not so crazy thick so you can actually wear it while moving at a decent pace.
I also have a piece by Marmot, but it might be Marmot Japan only – not sure.
Marmot Polartec Alpha Power Grid Vest.
Is is a vest with a very thin Alpha front, and a very thin Powerdry back.
Has a half zip and a kangaroo pocket. Weighs 154g in a (Japanese) Large.