You'll struggle to buy a new one. There's a couple of different heads, if it is the larger one, the belt number is 05276-01-0104 and we have a good used one. If it's a different one, let me know the number and I can look.
I am presuming you have stripped it down already and actually seen the snapped belt? Because they very seldom snap and the head not turning is usually related to the internal turbine breaking.