See here: http://www.defendersource.com/forum/...ght-63502.html
There is zero need to get a "genuine" belt. One belt is as good as the next.
You need to find the cause of the failure. Check that the alternator and water pump spin free. Buy two sets of belts.
The PS belt probably slipped from get covered in coolant, so just make sure it is tight.
Obviously top up the coolant and get extra.
Hopefully you did not kill the head. They do not take well to overheating.