It's the
Lowepro Lens Trekker 600.
I use one as well to carry my rig (D300 with grip, Sigma 500 4.5) around. It's a top/front loading backpack with good straps and waist belt. Loops allow for additional bags (lenscases) to be straped on, and there is a tripod carrier as well. The Lowepro website shows all the details to give an expression how this works.
The combo fits assembled into the bag (body on lens and lenshood in working orientation on lens) with about 15-20cm extra space on the top. That's where the flash travels. I can leave the flash bracket and flash cord attached to the lens foot, but depending on the flash bracket design that may become a tight fit.
By nature its a pretty bulky pack, but you are pretty much ready to shoot when you pull your rig out. Just clamp it to the tripod/monopod and you are good to go. Takes me longer to strap the Better Beamer to the flash and get this conception attached.
I think that there are one or two similar solutions by competitors (Think Tank, Kinesis?) that are similar in dimensions but not neccessarily in price and local availability).
Ulli