I laughed at Jeffy's response...
Back when we were kids, before all these new fangled products came out, I would carefully back up, and then PUNCH IT! and get all the water to go back onto the duster. The front of the duster has a slight rise to it, so upon further acceleration or turning; most of it would splash out.
But here's what I thought about doing...
Get some 2" or 2.5" PVC 'T' connector, maybe with a 1" inlet. (I hope I'm describing it correctly) 2-2" and 1-1"... Cut the bottom half off of two of them...
Then measure the width, add a little for a rise and epoxy in that 1" rod. Spray it black... It sits taunt between the side spreaders and it's easily removable... Maybe get a small tube that has a 1" ID and meet those to pieces in the middle. Simple and maybe $5.00 worth.
*Patent pending!!