Your local feed store might have it. Mine does. Also wheat is probably the way to go for fodder in my opinion. Barley seems more finicky and gets moldy easier. Yeah health food stores are going to be really expensive. Here in Texas I got a 50 pound bag for $14.00 at my local feed store. Call around, one of your feed stores most likely has it!
This is where I got my barley. $10 for one pound, but it gets a lot cheaper per pound if you order 2 or 5. Since I was doing an experiment, I started with one. I left the review, and am very happy with my results. (No, not getting anything for saying this or for my review. ) Oh, shipping was included too. I used to work in shipping, and I know what it costs.
It is a lot more than the $14/50 lb bag people are mentioning, but I couldn't find any other barley for fodder. I also don't need 50 pounds of barley sitting around attracting mice or taking up space in my garden shed.
For reference, a pound is about 2-3/4 to 3 cups of barley seeds.