Sorry for some reason it wasn't included in the title but I believe this is the font used on 2008+ REV-XPs I'm not sure about other years. I know my bro's 2003 H.O. is different.
I spent quite a bit of time looking for a font for my custom registration numbers. In Ontario you can put your own numbers on instead of using the "sticker plate". On http://www.findmyfonts.com/, the best match I could find is "vipnagorgialla". The font has to be sretched & compressed a bit until you get the square looking zeros though.
I've attached the actual 500ss from the sled as well as the Font. You can see the "SS"'s are a little off, but I think that's because I had to compress the height to get the zero's right.
If anyone knows of a better match let me know! You can see without the border it's a much better match, but I need something around it as I'm putting these on a yellow hood.