You don't need a Datcon gauge. All you need is one that's the same size and type. Any auto parts store would have one. There are two basic types...mechanical and electrical. If yours has a small air tube coming into the rear of the gauge, it's a mechanical type. If there are only wires, it's an electrical type. An electric gauge has two elements...the gauge and a sending unit. The sending unit will sometimes die on you. It is screwed into the engine block, usually on the top of the engine somewhere and goes into the water jacket/coolant system. If you get a new gauge, it should come with a sending unit, so you should be able to tell what they look like. Also, sometimes, gauge failures are due to a faulty ground somewhere, so you might want to check your ground connection to the meter first.
2004 Tiffin Allegro 27.5 ft. P32 18,000 lb GVW. 8.1 liter. Workhorse chassis built May 2002. 21,000 miles. 2012 Jeep Liberty Toad. RVi2 brake unit.