We can have your instrument rebuilt to "as new" condition. You can send us your rebuildable  gauge, if it cannot be rebuilt we might have a good core on our core shelf, for a fee naturally. Since Smith Instrument does dot make new gauges for our cars this is the route to go. You might be able to find a good used one but how long it will last nobody can say. We are dealing old cars. 
You can give us a call for an estimate of the cost.