This is what I used for the Camino Portuguese I just finished.
http://www.containerstore.com/shop?productId=10035589&N=&Ntt=reisenthel+laundry+bag
My journey included five air segments, both intercontinental (US to Europe) and within Europe. It worked perfectly and is distinctive on baggage carousels.
I just pulled the cords shut, attached a luggage tag and double knotted a bow - like tieing shoes. Plus, it folds down to about the size of a deck of playing cards, weighs less than that and is easily machine or hand washable. I just threw mine in a washing machine as the chance presented itself.
This particular bag is available in varied patterns and colors from this source. I chose the green as it matched my rucksack.
BTW, it easily held my Osprey Kestrel 48 liter pack fully loaded, I mean fully overloaded...but that is another story...
I hope this helps.