Good info in that link. Here are others as well.
I have gotten good use out of a SeaQuest Passport travel BC. Mine is a medium and weighs 5.73 lbs. ( 2.59 kg) with a SeaQuest Air Source attached. It even has an integral mesh bag for packing.
I know the Zeagle Scouts are very light also. The older ones at least are even lighter than the Passport. The new ones look excellent and well worth consideration.
But my current Travel BC is da bomb! Deep Sea Supply Kydex backplate with their 17 lb, (lift), TTW-17 Tropical Travel Wing, a one piece "Hog" harness and a couple of weight pockets, weighing at at 3.08 lbs. (1.4 kg.) It packs up incredibly tight, is very streamlined in the water and dives like a dream! It is actually a little negative in it's inherent buoyancy. If I needed more lift I could just add a larger wing.
This may not be the best solution for everyone, but it works great for me.
-Thomjinx