This topic came up on another forum, so I did some quick searching for a lightweight, portable travel chair. It's not ideal (won't fit well into luggage) but it is only 1.4 lbs and can support 300 lbs. And it's only $33, not bad.
http://www.amazon.com/Roll-Mobility-.../dp/B004S76AGO
http://www.amazon.com/Roll-Mobility-.../dp/B004S76AGO