Before Soundboks went industrial they made portable speakers for festival goers by hooking a speaker up to car batteries and putting it in a nice box. I imagine you can get a nice setup following their footsteps. Unfortunately Soundboks is more than twice your budget so I can’t recommend them on that alone, but a cheap second-hand speaker (or some drivers and an empty box so you can fit batteries inside too), a car battery, and a cheap microphone should be doable below €200-€300.
Before Soundboks went industrial they made portable speakers for festival goers by hooking a speaker up to car batteries and putting it in a nice box. I imagine you can get a nice setup following their footsteps. Unfortunately Soundboks is more than twice your budget so I can’t recommend them on that alone, but a cheap second-hand speaker (or some drivers and an empty box so you can fit batteries inside too), a car battery, and a cheap microphone should be doable below €200-€300.