Have you been using ATF in the Power Steering system? Just curious.
You need to wash the pump really well at the coin carwash and watch closely to ensure that it is indeed the pump leaking, then get a wrecking yard pump for about $125.
Use regular power steering fluid from the auto supply. It costs less than $3 per quart and works great. That's what I've used in my 240D p/s system for the last 400,000 miles with absolutely no ill effect.