Try calling Pioneer or Pioneer Parts Dept.
It's not a downloadable item, unless someone has ripped it and put on an illegal DL site. But even if I knew of such a site, which I don't, I wouldn't tell where. I'd think you can get one either no charge or not much money by calling Pioneer, especially if you provide proof that you bought an open box item from a authorized dealer. If you didn't buy it from an auth dealer, then they have no obligation to send you one unless you pay for it through their Parts Dept.