If live-streaming isn't your focus and you're only doing the occasional live-stream, or especially if it's just this once, then a cheap headphone splitter to plug your mic in will be more than sufficient. It will be a bottleneck compared to USB quality, but you should still sound as good as 3.5mm will get. It doesn't sound like what you're doing will justify a "proper" audio setup; it's nice to sound nice, and it impresses people, but a splitter is a good-enough compromise if that's easier for you.