I recently purchased a Small / Rectangular GPS Speedometer from Amazon, It plugs into a cigarette lighter, or can be wired direct to a 12 volt DC source. I attached it, with Velcro, to a bracket, that I made, and attached it to the steering column. I compared the speed to My Garmin GPS, and it read the same, at various speeds. It cost $39.xx, and it's a slick little item. .