You can check with Jim Snelson at Control Line Central. You can tag his homepage right from this site.
Also, like some others say, check your local sign shops that can do stuff in vinyl, (which is almost all of them anymore). The key is having a bit of artistic sense yourself and then being able to describe exactly what you're after, including required material types, to the sign maker who hopefully has some artistic sense as well. Unless you can show it to them and/or sketch it out, you need to be able to picture in you're head what you're after and be able to describe it in detail. I'm lucky to have a buddy that's in the business in my area. I just pencil sketch out what I'm after, give him dimensions, and he whips my stuff out.