WNY Supply has the ones they use in RPCs for a reasonable cost. Look on their website for these analog type volt meters. They are asian imports but WNY has enough confidence in them to use them in their own products.
I needed some smaller volt meters to make up a "tuner" for balancing phase converters and I found some cheap digital ones ($15 each), in an ebay store "Asia Engineer". These require no power supply when measuring voltages above 50 volts. I tested them out, put the RPC in the back of my truck, hauled it some 950 miles, reassembled the RPC, did a 3 hour demonstration and the all three voltmeters worked perfectly. These votmeters are not as rugged as I was wanting but they proved themselves to be serviceable.
These have a very short and very small gauge pigtail. I mounted a barrier strip ($3 at Radio Shack), just below the volt meters and terminated them there. I connected the larger wires to the other side of the barrier strip to be sure there is no strain on the volt meters. They snap into rectangular cutouts and I wanted them to me more secure so i caulked around them with silicone RTV which anchored them in just fine.
Bruce Norton
Kingsport, Tn