JBL Flip is quite popular due to their audio and build quality, that's paired with a relatively friendly price tag. As a plus, you can fix a lot of things about it - that's how I've been having mine for over 5 years now!
In this video you may see how you can replace the speakers in your Flip 4 - in case you haven't been careful enough while swapping your battery ;)
The replacement speakers are available on international marketplaces at a relatively good price.