For just $8-$15 plus shipping you can buy 84 feet of manhole cover cushion gasket rope at USAbluebook.com, sewershop.com, or several other sites. . However, I have a cheaper solution that cost me only $1.50 and did not require removal of the cover: Sand. However, there is a catch: The cover needs to be slightly undersized. In front of my home, NYC replaced a large sewer manhole with a made-in-India manhole cover. I will spare you the details regarding the primitive, below-standard, zero-safety, manufacturing process in India, but you can read about it online. In my street, as cars rolled over, the new cover would rock and make a surprisingly loud metal-on-metal, klunk-kunk sound that echoed between the houses. We also noticed that the cover was slightly undersized, leaving a noticeable gap around the rim. So we took advantage of that gap and packed it with sand. Each time a car drove over the manhole, the cover's rocking sifted the sand under and around the edge of the cover. The cover still makes a little noise, but the noise is about one-tenth as loud, since it is now metal-on-sand, not metal-on-metal. Next fall, I suspect that mud and leaves will begin to replace the sand, creating a mud gasket around and under the edge of the manhole cover.