Reddit mentions of Digital AV Audio Adapter, HDMI 4K Sync Screen Connector with Charging Port [Must be Powered]

Just find a decent looking 2.1 from a fairly reputable manufacturer. I believe Logitech and Edifier have a few sets in that price range. Don't expect anything mind blowing but I've had some of the cheaper Logitech sets and they're pretty good for the money. Try look for ones with the best reviews, look for common issues too.

Also consider going 2nd hand. PC speakers tend to go real cheap.

Alternatively, you could get a portable speaker like the Anker Premium. Many people say it holds up well against the Bose Soundlink mini which is a very impressive speaker for its size. Anker are great and very reliable.

In realtà non sacrifichi i cavi proprio per nulla, anzi: la cassa la devi comunque ricaricare e invece che fare un bel lavoro di cable management una volta per tutte ti tocca ogni volta o spostare la cassa da un'altra parte o attaccare un cavo volante.. Comunque io ho questa e mi trovo veramente bene!

https://www.amazon.co.uk/gp/aw/d/B0109TWZ54/ref=mp_s_a_1_3?ie=UTF8&qid=1493512140&sr=8-3&pi=AC_SX236_SY340_FMwebp_QL65&keywords=anker+bluetooth+speaker&dpPl=1&dpID=41Q-DurTe6L&ref=plSrch

If you want a portable one this is brilliant

For the price it's a top notch speaker. I decided to shell out just slight more and bought the Anker Premium Speaker. Half the price of the Bose Mini Very nearly as good It was was £54.99 when I bought it, looks like they sold out

[2015 New Release] Anker Stereo Wireless Bluetooth 4.0 Speaker (A3143), 20W Output from Two 10W Drivers, Dual Passive Radiators / Subwoofers for Bass, 8-hour Playtime, Portable Bluetooth Speaker for iPhone, iPad, Samsung, Nexus, HTC and More https://www.amazon.co.uk/dp/B0109TWZ54/ref=cm_sw_r_other_awd_ieh-wb3CKAD6K