Not really aware of anyone selling already made signs. Micron Arts used to sell a small brass kit of railroad crossing signs - you might be able to find a set on an auction site - they're out of business now. If you have access to Adobe PS, Corel, MS Word.... there are some sites you can download, scale down the sign and make your own - just cut the head off of a pin and mount the sign to it and voilá. Just as a disclaimer, I have no affiliation to these sites just merely giving you some options. Here are some sites that offer street signs: Modeljunkyard.com (road signs) - has a FREE tutorial on making metal signs out of beer/pop cans(geared to larger scales). I believe it's in 1/25 scale. Just convert it to Z scale and print on paper. Evandesigns.com (sign creator) - program will allow you to automatically scale down the sign to z scale and print - fee is charged for downloading their software. Hope this helps
The problem with printing your own Z scale street signs is that the resolution of laser or inkjet printers is usually not fine enough to deliver satisfying results in that scale. I've therefore been getting most of my Z scale street signs from a small German producer, Heinz O. Schramm/"HOS Modellbahntechnik". He has a large range of standard signs, including US ones, and is also happy to accommodate special requests. He uses a high resolution UV printing process and attaches the signs to etched bases; the results are really outstanding (see photo of a few US signs I've recently gotten from him). His website is German only (http://www.hos-modellbahntechnik.de/), but I guess that you can just send him a mail in English (HOS-Modellbahntechnik@web.de). By the way, he also has a lot of other nice Z scale accessories.
If a real-world sign is say . . . 18" (~1/2m), it would be o.08" (2mm). An everyday photo printer is 1400 dpi or 112 within the o.08" (2mm). Some can print up to ~10,000 interpolated, looking sharper, like the still-capture on the U-tube clip The issue is that most every one is using printed media copying (say, using a scanner), a photo of printed media or, with a web page which generally has highly compressed "jpeg-like" content. Or, designing in Bitmap ("Paint"). And, when done, reducing the images by 220x. This does not work. Using vector drawing (CAD, Corel, etc.), an entire locomotive could be printed sharp, if the printer can (like the UV one). So use a vector drawing program to start. Not sure if the Evans's design does. Most decals are super sharp and Robert Ray's Laser kit decals have quite readable [2" shoes] and all other rolling stock markings, printed by an Alps printer. Glossy photo paper (you can find thin sheets, compared to typical thick) and decal paper to
