Looking for the perfect bag

I might as well be looking for the elixir of life, but bear with me.

I'm looking for a bag that fits the following description:

• backpack

• side access to camera and two lens pockets

• some extra space for travel things - passport, lonely planet book, packed lunch, something warm, etc

• (optional) space for small laptop (11" MacBook Air or a regular netbook)

• as compact as possible - this is for travel.

• needs to fit:

• Mid-size DSLR (currently 7D) possibly with grip

• Canon 24-105mm f/4 L IS USM (83.5 x 107.0mm)

• Canon 200mm f/2.8 L II USM (83.2mm x 136.2mm) or one of the 70-300mm options.

• Canon 50mm f/1.8 II (68.2mm x 41.0mm)

• Sigma 10-20mm f/4-5.6 EX DC HSM (83.5mm x 81mm)

• Sigma 30mm f/1.4 EX DC HSM (76.6mm x 59mm)

(I am planning to get a 5DmkIII later on, so the two Sigma lenses will be replaced with suitable full frame lenses, but they will be of similar size)

Background:

After many years I've finally had to admit to myself that a shoulder bag just doesn't work with my physique. I spent the last weekend at a festival with a Thinktank Retrospective 20, my 7D, 24-105 f/4 L, 200mm f/2.8 L II and 50mm f/1.8. It's not exactly a mountain of kit, but I found that I had to have the camera hanging over one shoulder and the bag over the other, or my shoulders would be in pain pretty quickly (yes, this is the result of prior injuries).

I don't have this problem with any of my back-packs, even with a lot more kit. The bag I have that I like the most is the LowePro Fastpack 250. I like it specifically for the side access to the camera. I can slip off the right hand shoulder strap, swing the bag around and get the camera out in a few seconds. What I don't like is that anything else in the camera compartment requires opening the entire bag, which is much more cumbersome. I know the Fastpack 350 is bigger, but I've looked at it and it's not big enough.

So what I'm looking for is something similar, but that gives me access to at least two lenses from the side. I've looked through the catalogues of all the brands I know of. The closest thing I've found so far is the Kata 3N1-22 DL:

http://www.kata-bags.com/product/8374.85656.83220.0.0/KT%2BDL-3N1-22/_/3N1-22_DL_for_DSLR_wmid-range_zoom_lens%2B_3-4_lenses%2Bflash

Does anyone know if such a bag exists?

Thanks