Newegg.com - ASUS TF500-DOCK-GR Docking Station (Compatible w/ TF700T) - Gray
or Asus Keyboard Docking Station TF700T-DOCK-GR - Best Buy
Neither of those look like the dock for the Prime. One is for TF500 which is compatible with the TF700T. The other is for the TF700T. Just look for a TF201 dock.