What you can do is look at the players supported on https://www.rockbox.org/ (open-source alternative firmware for mp3 players) and check which ones are currently available for purchase somewhere. From the top of my head I know at least Surfans F20 and Xduoo X3II shouldn't be hard to come by.
I couldn't second that more. Rockbox is a wonderful 100% FOSS operating system for music players, and they're working hard to port it to new devices, almost always with zero help from manufacturers. HNers, please consider donating to the project, and/or if you have a old player collecting dust somewhere, also consider donating it to them so they'll have more hardware available for testing; when working with undocumented platforms the risk of bricking them is high, so it would help a lot.
It warms my heart to see Rockbox still alive and kicking. Most of my experience with it took place around 2005-2007 (wow, we're getting old I guess!). Great project.
