Reddit mentions of Belkin F3U134B06 Pro Series 6-Foot USB Extension Cable

Sure. A good starting point is actually Zoom's "Recommended Hardware" section on their website. Most everything on that site can be purchased separately.

> I need to buy a HD wireless webcam...

I don't think you actually do. First off, wireless webcams for what you're trying to do are not really a thing. And even if you bought one that claims to be wireless within your budget, I guarantee that you'll have reliability issues with it: it'll drop out halfway through the broadcast, it won't pair, it just won't work, etc.

Instead, I'd recommend getting a Logitech c930 and stick it on a tri-pod. It's a 1080p wide-angle webcam -- it'll work great for short or medium distance viewing angles. Buy a USB extension if you need more length, but be careful, USB cables tend to start flaking out if they're longer than ~10 ft.

As for audio, it depends on what the audience needs to hear. Will he only be talking with them? Will he be playing an instrument as well? There are a number of options here, so I'll need a better idea of what's going on to recommend the best solution.