Harris Regulator Repairs

[Mal g]

After 6 months of planning, I finally got serious and used my keg set up for a quite drink over the Christmas hol's, all went well except for the Harris 601 regulator, which I got second hand, still in it's box, from a friend of a friend, It will not zero out , the needle stops at 20 lbs, can I by a kit to repair it, or is there a place who will repair it in or about the Sydney area?. I worked out a system so I would'nt waste the beer but it was'nt brilliant a bit like a pommy beer