Yeah, you can't donate directly to the official campaign if you aren't a US Citizen.
I'm not a part of it, but on the Ron Paul forums, we have a New Hampshire flyer fund-raising drive. It's separate from the official campaign:
http://www.ronpaulforums.com/showthread.php?t=21847
Or you can go to ronpaul.meetup.com and find a city you like and donate to their campaign by contacting the organizer.