Sony's powerful yet very small XB10 Bluetooth speaker is currently under $50 over on Amazon. This is a great price for what you're getting here with the XB10, it's also part of the company's EXTRA BASS series of speakers and headphones. So it'll offer plenty of bass and great audio overall.
The Sony XB10 here is the 2017 model of the popular Bluetooth speaker. It's currently Amazon's most popular Bluetooth speaker under $100, and it's actually under $50 right now. It's somewhat small, but offers some amazing sounding audio, but then again, that is what you expect from a company like Sony anyways. Sony does allow users to pair two XB10 speakers together and offer up stereo sound out of their music. Surprisingly, the XB10 offers up to 16 hours of playback, which is more than most Bluetooth speakers, and somehow Sony has crammed it into a small one here. This also has NFC which makes it easier to pair with your smartphone (unless of course you have an iPhone). Sony offers the XB10 in a few colors including black, blue, red, and grey, all of which - at the time of writing this, at least - are priced at $48.
It's also eligible for Amazon Prime's free shipping. If you are not a member of Amazon Prime, you can sign up for a free 30-day trial and take advantage of unlimited two-day shipping as well as the many other perks that Amazon Prime includes.