Can you make fish broth with just fish flesh — no bones or heads?
Fish broth, like most stocks (except vegetarian), is almost always made from bones, and usually includes other parts of the fish like heads, tails, and fins. In addition to the flavor and protein from the fish bits, you need the gelatin from the bones to give the stock &quot;body&quot; and texture.
I also live in the US, and there's a very simple way to get the heads, frames (bones), and tails: buy a whole fish and fillet it yourself.  You make a stock from the frame and use the meat for the soup.
If that freaks you out, or you live in one of those midwestern towns where you can't get whole fish, here's a workaround.  It has decent flavor, even if it lacks some of the body of a proper fish stock: make a broth using dried scallops.  You'll probably have to order them online, but they ship well.