I only know of 3 alum pulley sources: URO (the forever back ordered one), ECS and Ebay. If I was ordering the parts today I would be inclined to go with the OEM Febi one. If you are using the Stewart WP, then the ECS should not be as much of a concern as the pumping efficiency of the Stewart pump is higher then stock so with the ECS pulley you will get that same pumping effect at idle but with less *effort*.
BTW, I've heard less than ideal things about URO, but not about the pulley specifically.
2004 ZHP * IMOLAROT II * OEM Clears * ///M Strut * CoolantSnitch