What you want are the real live Kefir grains so you can keep making kefir forever for free. So called "starters" only contain enough for a few batches.
I bought some on ebay. My advice would be to look for a seller near you (so it doesn't have to spend a week in the mail) and make sure they have a good feedback score so you can trust them. Or if you don't like ebay find a kefir list and ask for someone near you that has some grains to share. Usually they want at least $5 for shipping so I found it wasn't that much more to just buy it off ebay.
My experience was that the ebay seller was much closer to me than anyone I could find on a kefir list. My grains arrived in one day and were so fresh I was drinking real kefir the very next day.