I have Sidewinder that does not have a mast collar. Rather, I have a Sidewinder and pieces of the mast collar. As a temporary fix I've put a 3 inch Fernco plumbing adapter over the mast. I think that should stop abrasion on the mast step.
This seems to be a common situation with these boats. I could have a machine shop turn one for except that would be at least $200. I'm interest in learning how others have dealt with broken mast collars.
Walter