But...
Do you want tin (commonly sold as 'tin'), or do you want tinned steel (commonly sold as 'tin'). That 1 gallon fuel can is made of tinned steel, if you can find metal fuel cans any more. My Perfect brand fuel tanks certainly attract magnets, so they're plated steel.
McMaster sells tin, and I think they mean tin, not tinned steel. K&S sells tin, but I'm not sure at all whether they mean pure tin or tinned steel, nor, for that matter, do I have any confidence that they know themselves.
Is there any reason not to use brass sheet?