Most headsets come with omnidirectional microphones. Even some "noise cancelling" microphones are actually omnidirectional, just with an arm long enough to be reasonably close to the mouth. When I recently decided I need a cardioid microphone on my headset, I've ended up spending about $300 total.
AT BPHS1. That has an XLR connector, so I also got a Scarlett Solo. I also recommend replacement cushions, e.g. from Brainwavz, as the stock ones are for people with some tiny ears (my ears hurt pretty badly after a long stream of meetings).
I've heard good things about Sennheiser PC 8 for tighter budgets, but haven't tried personally.