U.S. Route shields
Templates for making new shields
Not for use on Wikipedia!
Get the Roadgeek 2005 Fonts and then just edit these in your favorite SVG editor (here at WikiProject U.S. Roads on Wikipedia, we recommend Inkscape.), and then change all text objects to paths. Then save it as a plain SVG. That should be safe to upload to the Commons as US X.svg or US X (CA).svg. Then use that in Wikipedia. You should also add it to the list above.
If do not want to make a shield using the SVG templates above, you can try asking someone to make one for you on the request page on Wikipedia. Just be very clear about what # and if it is California style or not. Right now, you need to wait for a human to fulfill your request.