Drain plug "ball"

My Daysailer III is missing the little "ball" in the drain plug. Heck of a leak without it! Does anyone know where I can get one or what the diameter of the ball is? I assume any ball that floats of the right diameter would work? Right? Wrong?
Thanks.
Ray Seligman (ssscomp-at-nycap.rr.com)
Thanks.
Ray Seligman (ssscomp-at-nycap.rr.com)