How convert Jukebox to MP3 without using wallbox

Hi All,
I wish to convert a Wurlitzer jukebox to play MP3's from the original key selectors.
Everything should remain inside the box. Only the keys and amplifier/speakers are used plus a 2 digit LED display
to give information to the user. No wallbox is needed and the aim is to give the impression that everything is original.
I was wondering if there was a commercial device that I could purchase, rather than having to design it myself.