I think the replacement pump for that would be a sedra 5000 or something like that (although it might have a fancy needle impeller). I've got a dolphin pump on mine but they don't make them anymore. You could also try an Eheim 1260.
EuroReef is now Reef Dynamics so you could contact them and find out what pump would be appropriate.
http://www.reefdynamics.com/category-s/54.htm