The Tow bar cost various from dealer to dealer, the best thing to do (as always) call a few dealers and get quotes. At the same time ask them whats the best price you can do on the Tow bar... theres a good chance they might give you a better price... FYI - You can also have a look at this Thread regarding tow bars for Aurion. might be useful....
Are you able to pair any other phones to the head unit? If the phone is still under a 2 year Contract take it back to Telstra and tell them the bluetooth is faulty.