I have installed a set of aftermarket mud flaps and they came with new push in retaining plugs like the original that hold the inner plastic fender well and so far they have stayed on through multiple automatic car washes
I bought mine off eBay for $350.00 and it’s working good for me. Not watertight but manageable . Aluminum honeycomb material that is textured gloss black. Cleans easy 1 year warranty. I have had mine for 6 months and 10,000 miles with no issues. Not sure if load limits but I wouldn’t stand on it...