Suggestions for amplify lead singer at a camp fire

Hi, maybe you can help me with some tech suggestions. At my local scouts troop I'm one of only a few guitar players. At camp fires I play the guitar and provide lead vocals, so that others can follow (which is important especially for songs, that are not well known). Because only a few can sit directly beside me and others might talk in parallel, I need to sing very loud, to give an orientation, which makes me hoarse way faster.

I would like to have something, that amplifies my voice, with decent quality (so no megaphone), a microphone fixed to my clothes or my head (as I need to play the guitar in parallel) and being portable (easy to carry, relatively small and powered via battery). I am able to spend like 200€ for it (300€ would be the hard upper limit). I can also build something myself, though I would need orientation on what to build exactly. I don't have experience with audio electronics, but with microcontrollers.

Thanks in advance for your help!