Seal the final pot connection

Hello guys I bought a motorcycle again after almost 30 years break. CB600 Hornet. 2008. Has a end pot from Leovince and the whole exhaust system is not original either. I have the original but (hopefully complete). I am here in Spain. Salesman meant to check the original end pot for a little bit. I tried this today ma because I don’t necessarily like the louder Leovince pot anyway. As almost feared, the original pot does not fit Although there was such a ‘dichtring’ there, the connection of the original pot is much too big, even if I pull the clamp very tightly I can twist the exhaust without any effort on the pipe and of course he ‘puffs’ out there as well. So back and again the Leovince put on it. While dismantling pieces of a tape have fallen out, some aluminum tape … now of course the Leovince is no longer dense. So probably my question, I have been looking for almost hours what the woh l for a tape could be what you use for sealing, but I find only tapes for repairing defective exhausts or for wrapping pipes. What do I need to look for?