We finally got Illinois Pet Friendly Plates for our car, it's $40 well spent as "Proceeds from these plates goes into a pet overpopulation fund toprovide money for spaying and neutering Illinois Companion animals." It was very easy to do...visit the Illinois Secretary of State site to find out how you can get yours. I would love to contribute art work if they ever go for a redesign!
If you live in another state visit PALC to see if your state has or is working on getting a Pet Friendly plate program.