How can I make a small Piezo Police siren, on a small footprint for HO Scale Model Railroad.? Police cars, ambulance etc

I have taken a little ambulance apart, which has a little piezo siren and flashing lights. I can create the flashing light circuit but how can I get the siren circuit ..?

HarrisCreekCentral (author) 7 years ago
That is fine for this one unit..   I would like to make additional sirens and flashing liights in other units.   Fire trucks, etc etc..  Flashing lights I have mastered,  but where can I find those miniature siren components.  Or is it possible to make them myself.?
Thanks for any ideas.
So the original model had a circuit that drove the two parts ? What's wrong with using that ?