First, you didn't have to take the pulley off. The power steering pump pulley has holes in it so you can get to the two 13mm bolts that hold the pump to the block off to do the water pump. But, since you took the pulley off, I once made the same mistake. Luckily my motor was out of the car at the time. You should be able to find a bolt to thread into the pump shaft, then use a nut and some washers to press the pulley on