[Alan Brinton]

Those are the part to which the mouthpiece attaches, Stuart. If the mouthpiece itself creates a good seal, then these parts are still usable. I doubt that a new replacement for the part shown in your photos is available. The mouthpiece itself is available, but at exorbitant prices ($20 or more). The old vintage models HM-901 and 902 are abundant on eBay at reasonable prices. You’d probably do better by searching “vintage melodica” on eBay and buying a complete melodica (sometimes with two mouthpieces) that’s in better condition than the ones you have.

Amazon: https://amzn.to/2NWybGZ