Alternative to pusher chatkit for simple chatrooms

Hi all. We have a need for basic chatroom functionality in our e-learning app.

Essentially we are hosting livestream content (a few rooms, each being a page with a 3rd party embeded video stream), and need to add a basic chat component to each page. Users (pages are behind Auth so users are know at this point) can chat in the room, room admins need to ability to do basic moderation (reply/hide/timeout/ban).

In the past, we built a similar system using pusher chatkit, but it seems that product has long since been depreciated.

I would prefer a hosted service, as chat is a small but important part of an otherwise fairly important event, so I could do without the pressure of it going wrong! And I would love to have the admin and moderation features come bundled. But am open to self hosting something. Some googling has found similar services, but they all require yearly contracts, and this is relatively one-off. We will be hosting this event for 4 days in September, and don't expect to do so again until next year, so a yearly contract seems rather wasteful.

Expected peak number of users is 750-1250 a day, split over 3-5 rooms.