You can spend as much as you want on a really good portable speaker by a brand such as B&O and if you do a lot of travelling, or want to use your laptop or tablet to screen movies, sports and shows regularly you may well want to invest. These will get you great sound anywhere. They weigh a bit more than the seriously mini speakers but they make up for it in quality of sound.
There are also some excellent tiny bluetooth speakers perfect for travel when you’re under weight restrictions. The sound won’t be as good as the ones above, but they’ll do the job very well.
Finally for those still addicted to their wired speakers I recommend these. Still going after all these years – the X Mini speakers which you can link together and plug into your device. They come in loads of different colours and screw down to make them even smaller for travel.