In reply to Martin1978:
I've got a North Face "HotShot" - ticks most of your boxes, inc padded laptop section and internal pockets. Might not be quite big enough, but, for example, I got the following in it last week:
Widescreen laptop, mouse, A4 work notebook and small pile of documents, shirt, jeans, pack towel and shower stuff, shorts, t-shirt, paddling cag, sandals, fleece jacket and freebie newspaper, with a little bit spare. Has some straps, so you could get the fleece outside.
All that for £8 in Phnom Penh