My laptop is 12.1" so it's much smaller than Computrekker's laotop bay, so
I don't really need that large computrekker. Maybe 30(W)*35(H)*15cm(D)
is enough for me, but be able to separate lens and laptop.
You may want to check out Tenba 12C shoulder bag (less than SGD120), made with very tough material, has a unique 4-way zip top opening. It has a 3-way access to your computer notebook. I already have a Tenba, else this could be my choice. I have a Lowepro trekker (mini) as well. http://www.tenbagear.com/products/2000_01.asp
Yeah, paddings are taking up much space in computrekker since they are so thick.
As for the Stealth Reporter 400AW and Tenba 12C, volume of both are okie. Dunno whether got add on strap which can convert them into backback. Back in school I used a backpack which had shoulder strap, for carrying books.
You would want to have a soft cloth inserted between the screen and keyboard of the laptop. I found out the hard way that having a laptop sandwiched between heavy camera equipment and your back can lead to scratching of the LCD screen.