I can tell you what came with mine, but that was almost 3 years ago, so it might have changed slightly.
I got the processor (of course), a package of batteries, a case to store the processor in, a jar of drying beads, a very soft toothbrush to clean the processor and abutment, a "leash" (basically a piece of fishing line with a clip on it so you can attach the line to your processor and the clip to your shirt so if it gets knocked off your head, you won't lose it), a little plastic thing so others can try to see what you hear when you have your BAHA on, and a little snap on cap that matches your processor that you can put on the abutment if you don't wear the processor. It keeps the abutment clean and also helps to hide the shiny silver thing stuck in the side of your head. I don't use mine.
As far as accessories, you can go right to the Cochlear Americas website and they have a list of what is available and the prices. My audiologist in Nashville also had some stocked at their office, but I don't think that's common.