rivets

One of my rivets has come lose on my FS650E, it's got the akra Ti, anyone know what size/type of rivets I need, or has any I can buy ? Many thanks . . .

I've been out on the bike a few times since it's now running fine but the rivets on the end cap have come loose with the exhaust pressure. I've been out to the garage tonight to remove the rivets and the end cap from the aluminium can. I seem to remember a post last year when someone recommended...