I have a clock from "Formotion" that is huge, about 40% larger face than most. It is easily readable by those who would normally need glasses. I have mine mounted on the handlebar, between the handlebar mounts. It is waterproof, etc. It is called the "Police SL" model and costs $98, but is worth every penny. I have the black face model. I special ordered it thru Fast Eddy.
ForMotion Police SL
