Some of those Marine tachs are pretty nice. They come many times with fancy beveled glass and have good outdoor seal protection. I like when gauges are in dashed or take the place of a stock gauge.

Another great place to find a tach is the wrecking yard. Almost every car has them and you could go and molest one out of another car and all you need is that one white wire to the coil to make it work. As long as pull the wiring from the car. Heck, you might even find a regular tach gauge there still in a car. Look in those older vehicles or ones owned by someone either then Grandma and Grandpa. I like lookin for weber carbs in wrecking yards, they are easy to rebuild and sell.