grand central at railfonts.com if you are really looking to get a font that is close. if you want to go the free route then you can probably draw them by hand or find a similar font and modify the outcome. contacting a historical society can sometime yield results. they might have a font, or a set of lettering diagrams for you to create lettering from. that is where i would start. most of the time when im trying to get the lettering right i find that it is better to draw them by hand. even the best fonts i think have differences on purpose to avoid any trademark infringements.
edit: later on i found one called Iris UPC - stretch it out and looks pretty close, good enough for a skin anyway.