[kaptain]

It could be a typical grommet and you might find that size at McMaster Carr, Graingers, or an electrical supply house.

Thank you for sharing your thoughts.
Both Amazon and eBay have many listings of rubber grommets and kits, I spent over an hour or two browsing through such listings, they seem for either electrical application or for pipeline water sealing, and I have no problem finding the 1-inch size diameter rubber grommets, but either their groves are too narrow, or grove edges too small, or hole too big, etc...