Are you just looking for a round type aftermarket gauge? I used Military WW2 style guages intended for Willys jeeps and trucks. The amp gauge has a vintage look and works for 6 or 12 volt. Here are several links. I used all five military style gauges in my 46 with a dash insert.

http://www.kaiserwillys.com/category/willys_ampgauges

http://store.midwestjeepwillys.com/640761.html