Why not just buy a portable CD player that plugs into the mains? their speakers are built in. Or are you looking for something more along the lines of plugging it into a guitar amp so you can really blast it out?
A really cheap laptop would do the trick and be useful for other things too, a second hand one could be had reasonably cheap. Just avoid windows 10 like a cholera-turd sandwich. Its a memory hog and infested with nasty and persistent 'phone home' and spying crap. In fact its so persistent in that, and in defeating attempts to get rid of it, I class it as malware, without doubt. Its malware with a few user features. Better, get linux. Free. If you buy a secondhand laptop or one without a HD, buy a hard drive separately (be aware, laptops need, well, laptop-sized (physically, without regard to disk space) HDs. In mine, its easy enough to change, it just comes out of the side without having to open it up.
