Attu

I did a quick oil change today and decided to fit a new alternator belt and Air con belt, the alternator belt came off easy but i didnt loosen the nut enough on the adjuster pully for the aircon belt and broke the plastic part of the adjuster ( the bit that the threaded bar goes through )
I quickly tightend the nut back up on the wheel and didnt end up changing that belt as id not be able to adjust it when i put the new one back on.
My main question is is this part (guess its the whole adjustable wheel part) avalable from Subaru or where can i get one 2nd hand ?? Ohhhh and how much ?

thanks

Andy