There's a hidden bonfire near the second bell. The spider thingy npc there can upgrade your flask. Of course you will need to go through blight town again but if you enter by the valley of drakes it's only a few minutes walk from firelink shrine.
The closest bonfire that I could find was just outside the hill, down just past the weird wooden elevator-type thing. The only other area I thought to explore (but didn't) was the area just below the room with the second bell; didn't want to risk the fall damage killing me right after getting 20k souls from Quelaag.
Where is this hidden bonfire?