Neoprene may cost the same, I'm not sure. In any case you could make a float of it. Cut a piece wide enough to go around the mast less the track, and about 2-3 ft tall. Glue this to the mast top.

I suppose if you can't find neoprene that's rather thick, you could laminate several layers. Just guessing, I'd think you want something on the order of 1/2 inch thick, more or less

good luck with it
tami