I got it from my local motor discount shop . They make a few sizes for thing like rover,jags,range rovers I think mine could have been a rangerover size. They just gave me a few blank ones to hold up to the car. I will measure it tomorrow and post.
I think that you should go to the police. With that photo and the time and date, there are probably other cameras in your area that picked up the van. Traffic cameras are great for picking up plate numbers.