Rick- look around for aircraft indicators. They are "28" volts, but will work just fine on 24.
If you absolutely need 12 volts, you can convert 24 to 12 with a 7812 voltage regulator. 7812's come in three main sizes, .1 amps, .5 amps and 3 amps. With either of the two larger sizes.. be sure to use a heat sink.
If possible use the aircraft parts.. those you just hook up and go.
D
"The best thing about building something new is either you succeed or learn something. Its a win-win situation."
--Greg Westbrook