I retract all my earlier statements. I was assuming it was the delrin ball on a post setup.
As was I. I think your best bet is going to be to convert to one of the other manufacturer's mast step systems.
If using the Nacra system (the one I'm most familiar with), it looks like any of the older Nacra mast bases will fit yours...maybe with a little work required. You'll then need to replace your dolphin striker post with the nacra post..and don't forget to make a spacer that goes inside the beam to keep the nacra post nuts from compressing the beam. You'll need:
Nacra mast base
Nacra mast ball
Dolphin striker post (goes through the main beam)
Two large nuts and washers to fit the dolphin striker post
spacer to go inside the beam to prevent compression
You may also need the aluminum plate that locks the dolphin striker post to the dolphin striker (not sure what you have there now).