While not directly a wireless dock adapter, the solution from 7dayshop could be a good alternative as it uses the 3.5mm aux in that is found on most sound systems and speaker docks. Plus it can even work in your car if your car stereo has aux in.
The beauty with solutions like the 7dayshop bluetooth stereo audio receiver is the wide compatibility range, even outside of the house. Simply plug it into the 3.5mm aux in port of your stereo, do a scan for the bluetooth device using your smarthone/tablet/computer, and you can start streaming straight away. God forbid you have purchased a new lightning speaker dock that does not have built in AirPlay or Bluetooth streaming, but should you have made that mistake, this little gadget could help you out.