I buy a lot on eBay and sometimes from the same sellers. Trainz sells on eBay too. I also buy on this forum and will be attending York. I also buy MTH tinplate from forum sponsors with websites. There are a few that are well stocked. There is also a train store in St Louis that specializes in postwar and prewar items. We have three good hobby shops in the Chicago area and a couple in Wisconsin, but not too much tinplate at those.
George