If this a piezoelectric beeper (AKA buzzer, but it really makes a beep) you can simply connect it in parallel with the indicator light on the dash. This is what I did on mine. They only pull a few milliamps, which is nothing compared to the light itself.
I suppose I could have made a delay circuit as suggested, but I didn't. The more annoying, the less likely it will be forgotten. If it's too loud, you can reduce the voltage with a couple resistors or just put a piece of tape over part of the sound-output hole.