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.
Walnut Whip
Ken Livingstone famously said the London 2012 Summer Olympics will cost Londoners 38p per week (the price of a Walnut Whip)