http://www.laptopstu...p_Backpack_.htm
THIS ONE!!!
i love this one. its made of neoprene, i've ridden 25 miles in a
torrential downpour (all the way) and i had wrapped my laptop in clingfilm in case the bag got wet. after 25 miles of torrential downpourt (did i mention it rained torrentially all the way?) there was only a slight teensy weeniest bit of dampness just inside the zip, so pretty much about as waterproof as you can get (wish i could say that same about my waterproofs!!) and haven't felt the need to wrap my laptop in clingfilm since.
The whole bag is neoprene and once you are wearing it you can hardly feel the weight of the backpack, the straps are wide neoprene too and don't dig in or anything, comfiest rucksack i've ever worn. Honestly, i forget it's there and it doesn't shift around. i got a medium and my laptop is 17 inch, i'm a six foot girl but i would recommend if your a big bloke (rugby player build) get a large as it will fit your back better, if your a skinny (cyclist build) bloke get a medium.
only downside is that you can only get your laptop and powerlead/mouse in, you can't carry much else in it but that is what i wanted (i didn't want to have the option of weighing myself down over 25 hilly miles so i opted for a bag where my only choice was to keep items to a minimum). so if you are only planning on carrying your laptop and power lead/mouse, go for this bag coz its brilliant. Also acts as a bullet proof vest (joking! but it does kinda look like one... you won't get shot in the back ha ha). has a secret pocket on the back and a pocket in one of the straps for your phone/keys (won't fit iphone tho, slim phone only)
can also be worn under your jacket... demo here from youtube by quite an annoying guy (so not obvious your carrying a laptop to wouldbe thieves if you cycle through dodgy areas ...
http://www.youtube.c...h?v=uAtSH0T14-A
Edit.. forgot to say, if your a girl the chest strap can be folded away and still the laptop doesn't shift around on your back. its brilliant.
further edit, after watching the youtube vid, i disagree with the guy on one thing, it does fit 17 inch laptops as mine is 17 inch. if you're unsure go for the large