You could get a 3V DC regulator that is hooked up to a 12V input, since there are plenty of 12V switched or unswitched wires in the car. However, would running another wire to the cruise control be conspicuous? There would also be the issue of wiring up the IC voltage regulator if you are not an "electronics" type of guy. It is cheap and easy to do if you are, but otherwise, not recommended.