I've mentioned them before, but I really like my Logitech V20 USB speakers.

https://www.cnet.com/reviews/logitech-v20-notebook-speakers-review/

https://www.amazon.com/Logitech-V20-Notebook-Speakers-Black/dp/B0009WKBGC

They are just small (and thin) enough to put into a laptop bag, but still have surprisingly good sound and enough oomph for their small size and being only USB-powered.

I've had one pair of those for like 14 years and they are still working great. I was sad to learn some years ago Logitech is not making them (or something similar) anymore so I searched for second-hand V20s, and bought two more pairs of them for small change. Now i have three of them and they are all in active use (one at my workplace and two at my home on two different laptops).

Nowadays if I try to find something "similar", they are usually wireless mono Bluetooth speakers, or then some very tiny USB laptop speakers. I have a couple of those Bluetooth speakers too, a Bose SoundLink Mini 2 and some cheapo I bought from Lidl. I am not expecting either of them to last 14 years, the batteries will die much sooner, and at least in the Bose they have apparently tried to make it hard or even impossible to replace the battery yourself (unless you buy a replacement battery from Bose, but they are not making that speaker anymore).