Looking for a Whistle
Prior to 1840, police carried hand rattlers that alerted colleagues to assist. In 1840, the whistle was devised and became the symbol of the British bobby. Finding authentic whistles can still be achieved. The whistles may be available from various sources and be either recently made or antique. Costs will depend on how old the item is, what it is made from and where it is purchased.
Online
EBay will no doubt have some bobby whistles for sale. If your search yields no suitable finds, you can opt for another online source. Cool Stuff Cheap sells authentic Bobby whistles at decent prices.
Constabulary Whistles
Certain makers of the time had contracts to make constabulary whistles with the name of the city constabulary either engraved or embossed onto the whistle. You may be able to locate a genuine constabulary whistle by contacting specialist companies.