Pump Cartridge replace

Joe_107

.....found a pump at a junkyard, a 3 speed 20/42. The cartridge was bad. Got it apart and thought about buying a new cartridge and saving the thing.
Haven't priced a cartridge yet- am I in for a shock? Also, who should I buy it from if it is feasable to rebuild the pump?
I'll check back for answers in a couple of days when I get back from work.