Maybe try an
Amcrest (rebranded Dahua) wifi indoor IP cam? Its got two way audio with an onboard mic and speaker. It also runs on a USB power adapter (although the actual power cable is a USB to barrel plug cable)
HTML:
https://amcrest.com/baby-monitors.html
Ignore the one that comes with a screen - it doesn't look to be a real IP cam. They're also readily available on Amazon.
I've got the 720p model and I'm pretty satisfied with it.
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I used HTML BBcode because the forum changes a url link is automatically into the target web page's title, making it look like an ad inserted into the middle of my reply...