We have this one http://www.toysrus.com/product/index.jsp?productId=2301479
It is extremely light and DH was able to carry TJ around the Cape May Zoo all day long.
HTH!
This is the one we have. I don't use it but DH does and he says its great.
http://www.kelty.com/kelty/kids.php?type=&cat=48&ref=&id=339