Best camera bag / backpack for a 1D?

I do a lot of event photography and I usually carry my stuff with me. My current camera bag is no good for my big, beefy 1D and a lens, I'm looking for a backpack kind of back that could easily fit a 1D and a few lenses and a flash, but also look inconspicuous enough that it doesn't stand out? And maybe not all that bulky?

I'm not looking to spend much unless I have to, but what would you guys suggest?

I use my ThinkTank Glass Taxi to carry my 1D all the time. It is a very narrow backpack and works great. Can get them used here for around $100.

Domke makes their F2 and F3 bags in backpack versions, with a lower camera compartment sized like the shoulder bags are and an upper storage space for whatever else. Very low key and very comfortable.

The Canon backpack is cheap and will fit your gear.