I think I paid $12 for the set of 6 from heart of texas offroad. Give them a call on the toll free number and he can tell you how much the shipping will be. I know what you mean about shipping charges...SOR reams you a new one on shipping. Thats not the case with heart of texas offroad.
Just make them from a piece of rubber thick enough that it's hard to get through the slots. I made mine about a half inch wide and long enough to snake through all four slots. I have a friend who used some small diameter motorcycle fuel line. 2 bucks instead of 20 and no waiting for shipping.