I've ordered from both Nitron Industries (
http://www.gardeniq.com/store/produc...al,176,94.aspx) and Fedco (
http://www.fedcoseeds.com/ogs/search...m=8731&index=4).
Kelp meal is comparatively expensive and, of course, shipping 50 lb. bags anywhere is pricey. Kelp meal is used as a feed additive for livestock, so you might try local feed stores. Here's one in Athens:
Mary's Tack & Feed:
http://www.marystackfeedpet.com/index.htm
This site lists a few more.
http://www.polocenter.com/health/feedusga.htm