I disagree on size. You need a bag or something to carry a 7", anything you can fit that into a 10" or even bigger would fit. 10" still easily fits on to train back of seat trays and the like and is far better for web browsing and film watching. 10" is probably the most ideal size you can get.
You do NOT need a bag for a 7 inch tablet, my Flyer fits in my jacket inside pocket and I travel on the train with it every week while my larger tablets gather dust at home. Do you want a pic? Stop talking rubbish.

(those waterproof/tough microSD cards are useful here too)

