Looking for advice please on what sort of microphone I need for the following setup:

Windows 10 laptop running powerpoint or playing videos...

HDMI connection to projector which outputs sound to an amplifier and speakers...

... and I'd like a microphone where I can speak and have sound output to same amplifier and speakers

... so two audio sources, powerpoint or video playing on laptop, and a microphone, going to the HDMI audio output.

I would pause the video or powerpoint before speaking.

Ideally the microphone would be muted by default and I would have to press something to activate it for when I speak, and unpress to mute it again.

Is this possible, and will it cost the earth?