There is a backpack bag for the 24"-wheeled Airnimal bikes, the wheels are however carried in a separate bag. The Airnimal website is rubbish for details of accessories but I found this about the 'carry-on' bag :
http://www.foldingbikes.co.uk/airnimal_bags_cases.htm
The Carradice website has hassles too, the folding bike bag main page shows a rucksack but the specific pages for the bag has either 'photo not available' or a picture of the shoulder bike bag.
http://www.carradice.co.uk/folding-bags/index.html
Your blog has pictures of a Montague Paratrooper but Montague (or Swissbikes) seems to only sell a cutdown version of an airline bag. Perhaps the backpack pictured isn't available to the public?