Pete is looking for an MP3 player because he doesn't know how to copy music to his Android phone. Leo says not many mp3 players are made these days. He can copy files on an Android phone by simply dragging and dropping when his phone is in transfer mode. It's called MTP mode. The phone will show up as a drive on his desktop and then he can drag and drop into the music folder of the phone.
If he still wants a standalone device, he could get the FiiO X1. It's around $100 on Amazon and it will play mp3s from a microSD card.