Are you sure you need them? They usually are found shinnied up the water tubes. Otherwise, I guess it is make your own. How about some milk jug and tie-wraps?
I see used ones on Ebay gong to a lot of money. And they really don't look like anything special either. I am certain a little ingenuity could make something else work perfectly. I know I would substitute something if I need them and they are no longer available. It is what iboaters do.
