It's not quite the same as a Stanley Knife, although I think they do make one. There are several makes of box-cutter, at the time the media showed a picture of the Pacific model which may or may not have been the one used. They are readily available at hardware and office stores and dirt cheap. US laws forbid the sale to minors (under-18), otherwise no restrictions.
Prior to Sep. 11 there was no ban on knives with blades less than 4 inches long being taken on board airliners. I had a box-cutter in my kit all the time - damn useful.
You can find pictures via a search engine, since most are commercial mail-order sites I can't post a URL here.