I bought a rubber mud flap for a trailer or farm truck at a farm store. One flap was big enough for both sides. I used a 1 inch piece of aluminum with four holes drilled through it to hold the mud flap to the fender. I also used panhead screws with cap nuts to hold everything in place. I placed the screws with the head against the aluminum that was against the rubber mud flap that was against the inside of the fender with the cap nuts on the outside of the fender. There is plenty of space between the tire and the screw heads that have a low profile and the cap nut (acorn nut) is a nice finish on the outside of the fender.
I choose rubber over a hard plastic mud flap because the rubber will flex if something hits it where I was afraid that the hard plastic mud flap might do damage to the fender if something was to hit it.
Good luck and I hope that this helps. Goose