Good photography backpack for travel?

I would like to find a back pack that I can take as a carry on to carry my Nikon D7000, 2 compact primes, and a zoom lens (possibly more, but probably not)
I would also like if it could carry a tripod and a smallish laptop ( not sure what model, I have a Asus G74sx which is out of the question for travel thanks to it's immense size)
It also must take accessories such as battery chargers and cleaning stuff, maybe a flash

And I would like one that isn't particularly easy to get into, because I'm going to italy in a tourist group and would prefer if none of my photography equipment were to get stolen from my backpack

Tenba makes great backpacks for photogear. A small one should hold everything that you are taking. They have sealed zippers, a rain cover and are very well made. At the pro level they are very popular.