Shepherd's whistle
They are also produced commercially. Simple whistles may cost less than 1 USD in bulk; expensive ones may be quite ornate. They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, Corian, jade, buffalo horn and other materials.
Falling Whistles
Falling Whistles is non-profit organization campaigning for peace in the Democratic Republic of the Congo. The whistle is a symbol of protest and the organization asks individuals to be whistleblowers for peace. The organization invests the proceeds from the whistle sales in Congolese visionaries, and are building a global coalition for peace.