(I know there are a few do-it-yourself options for these, but I'd much rather throw a bit of money at it rather than time).
Tested it without the headset in a Teams meeting and mutes within the meeting and displays status as such, doesn't just mute system mic volume. Edit: seems to work the same in Zoom as well.
The dongle itself is model ENC010 and looks to cost around U$50.
It has two down-sides:
1. Muting the mic involves touching/moving the mic, so you make some noise when trying to discretely mute/unmute.
2. It mutes, but doesn't tell Zoom that it's muted, so you can appear to be unmuted to others on the call. I'd rather die than be falsely accused of having a dog bark interrupt a call from MY mic!