How can I protect my Pop-up Camper from rocks/dirt?

Campfire Time wrote:
A common mod is to add diamond plate the front of the trailer. Some come with it already.

http://www.modmyrv.com/2008/06/30/rv-diamond-plate-rock-guard

diamond plate are great protecting the RV from rock damage, but I am looking for something that will keep my Pop-up clean.

I don't have any damage, it just that the pop-up is very dirty by the time I arrive to the destination....