Might've been an S1, which arguably was better than Apple's products in many ways, and likely sold a lot more: https://en.wikipedia.org/wiki/S1_MP3_player
From the Wikipedia page:
This product is what is referred to as a 'common mold' which means many different suppliers can produce this same model. The manufacturers are almost exclusively located in China.
Primarily defined by the use of a system-on-a-chip of one of the Actions brands and some common core features, S1 products vary widely in software and hardware as well as design.
I counted 62 different manufacturers listed in the Wikipedia article that apparently licensed this reference design (the core features and basic hardware), and who then made variations to the user interface or added a feature or two, and slapped their names onto it.
There seems to have been a whole industry of MP3 Players that were essentially identical at the core electronics level in the early 2000s, and we never realized it.