Blacknchrome......You can buy them anywhere, but if you can find a local OTR truck store, you;ll find them there at a very inexpensive price. The ones you want for your coach (to match the others) are the hard plastic models.
They're now selling mudflaps made out of a material that looks like the spiked RV door mats, like these Durascrape Mats - Product - Camping World
. You mount the spike side of the material forward. They do a great job of funneling the water straight to the ground.