When you fly on long haul flights, you always get a little "courtesy bag" of some type. They come in various shapes and sizes and all of them are handy little bags for camping and trekking. All of them come with a good travel toothbrush and a tube of toothpaste too. Oh yes, and earplugs are good for rainy nights.
A few that I have collected in my travels. Ask your friends to save them for you!
Top: (blue) Malaysian Airlines toilet bag. A nice little box shaped bag with a zipper lid and waterproof lining.
Top left: Virgin Atlantic shoe bag with a drawstring. Quite large, but the top can be folded down to make a smaller bag.
Purple right: Virgin Atlantic soft bag with press stud fold over flap.
Clear bag right middle: Virgin Atlantic Economy class - a great and strong ziplock bag. I like these!
Bottom right: United Airlines drawstring nylon bag.
Bottom Left: Continental Airlines. This one has two zippered inner compartments, a hanger, and the whole thing folds together and is fastened with a good zip.
Rod
A few that I have collected in my travels. Ask your friends to save them for you!

Top: (blue) Malaysian Airlines toilet bag. A nice little box shaped bag with a zipper lid and waterproof lining.
Top left: Virgin Atlantic shoe bag with a drawstring. Quite large, but the top can be folded down to make a smaller bag.
Purple right: Virgin Atlantic soft bag with press stud fold over flap.
Clear bag right middle: Virgin Atlantic Economy class - a great and strong ziplock bag. I like these!
Bottom right: United Airlines drawstring nylon bag.
Bottom Left: Continental Airlines. This one has two zippered inner compartments, a hanger, and the whole thing folds together and is fastened with a good zip.
Rod