Have you got or are you able to sort the right size mounts out?
Ash helped me sort the problem with my Falcon so bar maybe keeping a set for the SMK...
Not Charity but theres always the chance as people do collect them but Bargin as in Poundland etc, still occasionally get a tin and lighter together...
My Grandad was often to be found with a Golden Virginia tin in his pocket, I think he kept it once he gave up smoking but Grandmothers likely binned...
If the tin is sealed I don't think it's a problem at all, once the tin is open they will start to oxidise because it's a natural reaction, but again...