My dock adapter isn't included with the PowerDock.

The PowerDock uses Apple's Universal Dock, and includes the following dock adapters:

• Dock Adapter 9 for iPod classic 80GB and iPod with video (5th Generation) 30GB
• Dock Adapter 10 for iPod classic 160GB and iPod with video (5th Generation) 60GB & 80GB
• Dock Adapter 11 for iPod nano (2nd Generation)
• Dock Adapter 12 for iPhone (1st Generation)
• Dock Adapter 13 for iPod nano (3rd Generation)
• Dock Adapter 14 for iPod touch

If your iPod's adapter is not included with the PowerDock, or if you need more than one of the same type of adapter, your best bet is to use the dock adapter that was included with your iPod. You can purchase additional dock adapters from Apple.