They can probably order em, take em a part number, but they will probably charge a bit more for it, and take just as long as summit to get it. Something to be careful of on the powermaster starter (I have one, well 2, I had another given to me brandnew in box, same exact one I had bought like a week before grrrrr) is the little connector, where you put the wire for the switch.
On one of mine, when I tightened this nut, I spun the little stud, and it broke the soldering behind it, that connected the connector to the wire. I had to put the other starter on, and solder the connector on the first starter.