Power steering pump leak?
The o-ring is an odd size and you won't be able to get one at the local parts store. Regardless, you have to take the pump off to replace it, so you should probably just replace the whole thing with a rebuilt unit while you have it off.
Getting the pump off is a PITA. You do have to take the pulley off in order to get to the bolts. This requires a puller, which you can rent.




