The solid state voltage stabilizer is supposed to be the thing to get. I don't know if the original style is still available. I would say that after I replaced mine, my gauges seem to read lower than they did before - I don't know why yet. IIRC, I got it from Moss Motors. I don't think it matters which one you get but they are also available at Nisonger, an authorized Smiths dealer/restorer in the US.