My method, maybe not the cheapest, but works for me....I go through the Petroliana
category on eBay (I am looking for mostly defunct oil companies of a specific area
and time for my 1930's gas station models and bulk oil plants), find signs..also sometimes in collectors' sites, print them out, and then take the print, whatever size, into Staple's. Their print shop in the front of the store prints me a whole sheet of them in whatever size I want, often a couple of sheets in different sizes. And I think many can do this at home, even the sizing.