Check out Lowepro. I would have thought a micro trekker 200 would hold the camera, lens and a bit of lunch. I use this ruck sack for light camera and lens combinations D2X, 70-200 f2.8 and 28-70 f2.8. I have owned the rucksack since 2003 and its been in use every weekend and its without a scuff or pulled thread - they are very well made and worth the high price.
www.lowepro.com