Portable Compact Megaphone (10W) Voice or Siren with sliding volume control

Amazon

Powerful | Our compact megaphone produces sound that can range 600 metres Portable | Lightweight with foldable arm and convenient carrying strap Easy to use | Only 6 x AA batteries required (Alkaline based batteries recommend) Multipurpose | Event organizers, Law enforcement, Fire departments & rescue teams Volume | Adjust the volume to suite the environment with Rotary volume control

Boxed2Me

L10 megaphone 10W with siren A compact lightweight, but powerful megaphone. With its built-in 10W amplifier, sound can be projected up to 600m in ideal conditions. The megaphone also features a good quality built-in microphone, comfortable pistol grip handle, rotary volume control and a short carrying strap. Rotary volume control Carry strap included Voice or siren switch