If you have a farmer's market or some other place where you can find a congregation of local folks interested in healthy meat and milk, chances are you can find someone, or find someone who knows someone. And anyone who has kefir grains will probably have some to spare -- just like sourdough, they tend to grow faster than they can be dealt with, if you don't exercise a firm hand.
I've found folks via a local yahoo group, and I believe through the Kefir_Making yahoo group (or possibly
Real_Kefir_Making... I don't recall which was more popular at that point).
If all else fails, you can buy them in the US from
GEM Cultures. Never bought kefir grains from them, but I had good luck with their tempeh starter, and they were quite friendly.