Help With Bags!!!!!!!!!!?

Question

Hi, im going back to school in a couple of weeks and i need a new backpack but it needs to be a reasonable size as it has to fit books and a p.e kit! but theres a really really nice design bag http://direct.tesco.com/q/R.203-0904.aspx

but it wont fit because its for laptops and i have had a look on the website and you wont be able to fit hardly anything in it apart from laptops and its just to small. basically i would like that backpack in that size and in that design but instead of it being for laptops. anybody know how i can do it like design your own one or anybody know of a bag like it. i like the racing stripes!!!

please help btw i am a boy 15 years old LOL.

Cheers.