Ok so the gas cap came to me with the lock cylinder missing.
Instructions are on the site
here. Scroll down to find them. Follow them. Find a screwdriver that snuggly fits the screw. Use firm downward pressure during rotation. If they seem seized, use a small amount of penetrant around them, tap the head of the screwdriver with the shaft in each screw slot, then return in a few minutes and remove them. If the gasket is damaged, replace it. Replace the cap assembly exactly as removed—hinge toward the rear of the bike. Leave the baffle assembly where it is.
One source of other parts you might need is
here.
Lock cylinders usually come in groups of six from various BMW parts dealers. The same cylinder is used in the side cases. You might find a single somewhere.
