There are post card dispensing machines in every major
church and cathedral in Rome and London.  They dispense one
post card at a time, for the price of about a dollar, of paintings
and other important items in the cathedral.  I do not know of
any other such site in the US that has such a machine.
This may just be a place to start.
 
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Will Michels
Battleship TEXAS
Texas Parks & Wildlife Department
3527 Battleground Road
LaPorte, Texas 77571
USA
713.479.4062