Hi
Try the likes of VDO, or Faria, who do a range of gauges and appropriate senders.
I've only seen these dual function senders for oil pressure, never temperature, but you never know until you try...
If this doesn't work out, then how about old fashioned technology? A Murphy "switchgauge" is a completely mechanical device, using a bulb and capillary tube to operate a gauge, on the needle of which sits an electrical contact. There is a second contact on a user positioned arm, inside the instrument. When the needle touches the arm it makes a circuit, which you can use to energise a buzzer, or light a bulb, or both. Far easier to understand than to explain!
The only down-side is you need to find a way to accommodate the bulb, which is quite bulky.
If you can manage that, though, you end up with a "historic" looking instrument panel, in keeping with the Lister's appearance, as Murphy never updated the appearance of these instruments.
All the types I've mentioned are commonplace on boats, so a marine chandlers would be a good place to start the search.
Good luck
Sparks