I was thinking of something more along the lines of that flexible black plastic garden edging you see in the Lawn & Garden department. It's got a rounded edge on one side and a sharp straight one on the other - you could drill and then mount the rounded part to the underside of the front bumper fascia with a few screws, trim up the edges to make it look cleaner, and call it done for pretty cheap. Not sure how it'd hold up to heat, but it'd be a little more rigid than rubber/vinyl, anyway...