Don't know if it still exists, but its called Waschbar.
Waschbar still exists, yes, it's on the Ottenser Hauptstrasse (or whatever it turns into). Go out of Altona Bhf onto the Ott Hstr side (pedestrian area) and carry straight on. It's almost at the other end (10mins walk or so) on the right side, there are a fair few nice bars & cafes along that road.
There is another SB one if you turn left just at the end of the pedestrian bit, on the corner past the small platz-thingy, much closer but not so cool looking. Never used them though, but may be doing soon.