diaper backpacks?

OK, today I have been researching backpacks. Specifically baby diaper bag/backpack thingies. With my other kids, I just used a bag, a tote, you know-just your basic diaper bag. But everyone that has BTDT recommends using a backpack for the trip to free up your hands. Can you just see it? Money pouch/passport holder around the neck (under your clothes of course), backpack on the old back, baby on one hip (or even better-in the baby carrier strapped to my front), suitcase in one hand, and s-lady holding the other, with a backpack strapped to her back-pulling her suitcase behind. S and Bman will be shlepping all the rest. It should be comical, but I can see their point. At least it looks like we will be traveling in the summer now, so we can ditch the heavy coats. Anyway, you wouldn't think that it would be very hard to pin down a basic backpack/diaper bag. But... I want something that I can use as my carry-on for the flight to China. It needs to be a good size and of good quality, but also a good price. Then once we are there with babe-in arms, I will switch it over to the baby's diaper bag. Any good recommendations out there?