The stabiliser is 10v, and is common on many British cars using Smiths electrical gauges. As an alternative you can use a solid state 10v stabiliser from somewhere like Maplins - their reference is Voltage Regulator TS7810CZ (N38CA). I fitted one for the oil temperature gauge in our Minor (it is 1958, so doesn't have the later 'hot wire' fuel gauge).
I only fitted it because I thought the original 'interrupter' one was on the blink, as the reading was ~20°C too high, but the reading with the solid state regulator/stabiliser was very similar, and the actual solution was to recalibrate the needle position at 100°C within the gauge itself.