Need an audio player that loops forever

For a prototype, I need to use a MP3 player that meet these requirements:

• Loops a .mp3 file forever when turned on
• Can be plugged into a wall (no need to replace batteries)
• Have a 3.5mm or 6.35mm audio output
• If possible starts playing as soon as I plug it into the wall i.e no need to press the play button, select a playlist to play, etc

I thought of purchasing one of these old MP3 devices:

But I’m not sure it meets all of the above conditions

EDIT: Reason we need this: We have a device that streams audio to a hearing aid. This device shutsdown in 5 minutes if there is no audio i.e muted. But we have a specific case where we need it to be on forever, so we thought of a mp3 player that loops an audio file of 4m30s with a little beep at the end just to stimulate the streamer to stay on

Any recommendations?  

Thank you!