What I would do if I had to stay with that skimmer and a new pump was in my future:
remove the skimmer from the sump. Remove the dead pump. Remove the venturi cone. Get out the dremel, attach a sanding drum, and remove the restriction from the input port. (pictures will be posted when my wife gets home)
Order a new pump. Preferably an inexpensive one. One with a needle wheel and venturi would be great. The Octopus 1000 would work, maybe a resun, SeaLine SL-6520, or other cheap pump. Plumb the new cheap pump to the old now modified skimmer.
This won't give you a bubble king, ATI, or even a MSX. It should be adequate for your 55 though as long as it's not crammed with fish.