what size are the two pieces you need, we have rolls and rolls of it that scrap gets thrown out at work, ill try to get you some.... its like orange in 1/16\" to 3/16\" ish thicknesses.....
also i wonder if spraying that sound deadening ruber undercoating onto the rocker gard backs would do the job too- just a thought...
edit:
Link shows 6\"x62\", ill see what i can find