If you want something very simple, I think there's a planet bike model for like $40 that just has speed, odometer, and temp, but I'm pretty sure it's backlit.
http://www.amazon.com/Planet-Bike-9-.../dp/B000AO9R8C
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"