It you’re in the U.S., Paul, I can send you some gasket tape that might do the job. You’ll find my email address in my profile. If you decide to try leather, I suggest getting leather lacing from a craft store such as Hobby Lobby, Michael’s, etc. It comes in various widths and they can advise you as to what kind of glue to use. But gasket tape that adheres on one side is easier. I’ve used it it on several other melodicas though not on a Yamaha.