Ask HN: Portable 17" second monitor?

Has anyone here heard of such a thing as a truly portable second monitor?

I travel a lot but find it very difficult to do web work with only my 17" macbook pro, yet my 24" BenQ external monitor is a real pain to drag around, and either impossible or expensive/bulky to bring on flights. I'd love to have a second 17" screen, identical to the one in my MBP, that I could bring with me in my bag.

I tried a web search for this but couldn't find anything useful, so thought I'd check here.