Something like this can work, but it needs +12V.
https://www.amazon.com/VideoSecu-Sensitive-Microphone-Monitoring-Recording/dp/B004REA7MG
It's fine if you have a separate 12V for the camera, but not as convenient if you use PoE.
This specific model is OK for a quiet environment but the output is super-hot, so even with the camera audio input set to line level and the volume setting at minimum (1 out of 100) it will still overload (heavy clipping distortion) on any moderately loud sound. Also the audio output is a RCA jack so you need to make an adaptor if your input is just screw terminals.
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