Try calling around to your local feed mills and feed stores. Just tell them you're looking for a bag of fish meal for your chickens. If they say they don't carry it, ask them if they could order it for you. A lot of places can get things from their usual supplier of feed or feed ingredients...
Fertrell is well known for their feed ingredients. Here's a link to what they offer. You can try their "Locate a dealer" page on their web site. Usually you can find their products at a feed store or feed mill. Feed mills mix up feed recipes for people out of the ingredients they sell...