I remember about a million years ago or so I had a small handheld vacuum - battery powered - that came with a computer tool kit. It was OK; not too powerful, but then it didn't really need to be. There were better computer vacuums available but in those days I wasn’t spending a lot on those sort of things. Now, however, I don’t even see such animals around anymore.
Today I was swapping out both of my DVD drives and even though I do try to get into the case and clean up regularly, I can always find a few pockets of crud - mostly dust pulled in by the cooling fans or dust that just finds its way in through some vents - that manages to find a dead space and accumulate. I used a Black and Decker handheld rechargeable vacuum to get what I could, but those vacuums are just too large to really be able to get into the nooks and crannies where the dust hangs out. That cheap little battery-driven toy I had years ago did have a tiny little hose attachment that allowed me to get anywhere at all inside a computer case. Of course I also have an Electrolux canister vacuum with a hose, but that would be like a sledgehammer to kill a flea!
Using air dusters inside a case is kind of crazy - they just blast the dust all over the place, and none of it manages to find its way out. I save my air duster cans when they get really low-powered and I have occasionally used them inside the computer case: I hold the dust-buster vacuum, running, right up to the area I am going to dust and then aim the almost empty air duster and let 'er rip. The vacuum catches most of any dust that does kick up.
But I would love to have a little, battery-powered vacuum again that is made for inside computer cases. Does anyone know of any that are currently sold?