You have the very briefly used breathing gor-text vent screw.. They work fine and are a great idea.. as long as you don't tamper with it.. I had one on my 10' Mana and it was great.. But because people think they should be tight (like a normal vent screw) they worry that it has a slight wobbly feel (normal) and they try and tighten it and damage it.. Or they see bubbles coming from it while paddling (normal and nothing to worry about) and so Naish stopped using them and went back to the normal metal vent screw with a rubber o ring.. Naish offered a plain black plastic vent screw replacement for grey coloured gor-tex plug.. The plain black plastic vent screw plug has an o ring and works like a normal vent screw.. You just put it in.. tighten it up.. and leave it forever.. Naish sent me one of these blank plastic plugs but I never used it.. Not sure where it is now but if I can find it I'm happy to send it to you.. I'm sure if you contact Naish direct or have your local dealer to contact them they should be able to get one for you.