self bailer rubber gasket

Does anyone know where I can buy the rubber gasket for a the self bailer? APS (http://www.apsltd.com/c-6562-bailers-thru-hull-and-manual.aspx) only sells them as part of a $25 kit and I have already bought 1 $25 gasket and am hoping someone knows of a better source.

Thanks,
ben

You can try two things possibly. Topkayak or make your one with gasket material from a automotive store.