Hi wilfx, I basically went to a random LFS and asked for the smallest powerhead they had.
RIO MINI 50 AQUA PUMP POWER HEAD (69GPH) - is the one I think im using. All you are trying to do is provide some positive pressure to the reactor to keep effluent dripping out. Look for low wattage. An aqualifter might work, hell, if you position the reactor above your sump, and feed water into it, you can just siphon the effluent out.