American Marine Pinpoint AC Adapter Kit
Product Review (submitted on March 18, 2011):
I have two: one needed a touch of solder for a loose connection, the other was fine. While the pH readings dip when a new load is applied to a shared circuit, the readings quickly return to normal. The salinity monitor is not affected at all. One outlet supplies about 10 items with no problems in accuracy. (I wouldn't share it with a wavemaker where load changes were frequent though.) Run your pH cable away from other power cords. I think it's cheaper and better for the environment than replacing 9V batteries.