Cobra Navigator Rudder

I have a Cobra Navigator for fishing and SCUBA diving in Hawaii.  It's great, but we always have trade winds blowing and it just doesn't track well.  I read an article that mentioned a Navigator with a rudder being used by NorCal Kayak Anglers.  If anyone knows any details about how to do it, where to get it, or any info that can point me in the right direction I'd appreciate it.

Thanks
Terry

I have not seen this yak offered with a rudder.