That's a tall order. I think the 3 bikes you mentioned would all be close in weight to one another and none of them would be considered light. Bikes that are built for comfort and not for speed are heavier by necessity. Of the 3 picks the Belleville may be the heaviest with its steel frame, but it's hard to say - I've heard that mixte frames are inherently lighter. Some other choices you may want to consider are the Swobo Dixon; a solid bike with a good reputation (and not too far removed from a beach cruiser.) But if lightness is an issue, and a folder is out of the question, I think the Soma Buena Vista frameset would make a great basis for a nice bike. Of course, at $500 for the frameset alone you could easily spend more than you're budgeting for, but you sure would end up with a nice bike. Here's a picture of a single-speed setup, but a 3-speed build would be almost as easy and only a bit heavier:

Good luck and happy hunting!