You can also, depending on the padeye, drill out the holes to the next larger size rivet and reuse. To prevent the corrosion from happening (you are right, it is galvanic) you can use like metals or keep the metals separate. Since it sounds like the padeye sees a decent amount of stress I would not use aluminum rivets. You can use stainless steel with a rivet cover over it so it keep it away from the aluminum crossbar or you can use a Monel rivet. If you need to locate a place to buy the Monel rivet, here are a few mail order places: Jamestown Distributers or McMaster-Carr or Fastenal and finally Robnet.

Good luck and don't worry. You will be sailing soon.