+1 with the engine number....
There are a few online parts list "microfiche" - bookmarked at home and will post back later with the link to the one I used when I rebuilt the Clamshell...
If you are in even more of a hurry, based on your location both Mitchells In Renfrew, Yampower in Shettleston, Clyde Outboard Services (Port G) & there's an outboard shop in Fairlie as well.... one of them should be able to help!