Scrutable

Our local Astronomical Society has been meeting via Zoom since last year, but we are hoping that we can resume meeting 'in person' sometime soon, possibly as early as October.

However, because we have a number of members who are potentially vulnerable, we would like to be able to stream the meeting (the main content is usually a talk by a member or a guest speaker).

I expect we'll use software such as OBS to bring together the Audio and Video for streaming, we're looking at what's going to be a good microphone for the presenter to use.
Ideally, we'd want it to be wireless - and able to be fed into a laptop so that it can be mixed into the video / screen share feed from a webcam or similar before being streamed.

Anyone done this and has a reasonably priced suggestion that doesn't need a full mixing desk?

I haven't personally, but a Bluetooth lavalier mic is what I would look into investigate for that purpose. Google finds both some reputable brands and some cheap ones. It would connect directly to your computer's Bluetooth and not need a mixer.