Ok, just called the extreme toy store and asked them if I could buy one from them. They said that they couldn't sell them since their plates had the company name on them. But that they didn't get theirs from the DMV, they simply printed them out. Sooo, it does look like these just have to be printed out.
The guy even suggested that I just make my own. So that's what I'm going to do. Does anyone have a link to a picture of one of these signs? If so, I'd love to see it so I can copy it and print it. If not, that's cool, I'll just have to a scooter dealer and maybe take a pic of one or something. Thanks for all the help though, I appreciate it!