I did as SD suggested and bought some sweatpants from the thrift store. Cut the legs off above the knee, sewed in a hem top and bottom, added shoelaces as draw strings and slipped them over the fenders. My fenders were scratching the paint. Now they are not. I will wash them once in a while. $6.00 invested.
The people who find fault in what you build typically don't build anything at all.