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.
Whike
The Whike is sold directly to customers and is also available from some specialist suppliers. The Whike costs around €3500 for customers in the Netherlands (2010) with accessories available for additional cost. The Whike is also available for hire from several places. The Whike is now available in the UK and other European countries. Check their website for availability.