Serpentine/auxiliary belt pulley

Evening all, I've had a little catastrophe in my 300 tdi defender. The bearing in the serpentine/auxiliary belt pulley has seized which in itself isn't a problem but the bolt that secures it too the tensioner has snapped. Is the bolt itself available or do I have to buy a new pulley or a complete new unit??

its not listed as a separate part and is a lh thread iirc

It certainly is a left handed thread, odd pitch on the thread too which doesn't match anything I've got to put in its place.