Generally any stereo has RCA inputs but not always 3.5mm Aux input jacks, for that you can buy a adapter "RCA to 3.5mm" to work with just about anything. For a cheap jukebox any old Phone with a SD card or Android box can be made with Kodi to be controllable with a Smartphone and store/play anything you want.
You will need something that has RCA red/white output to connect to the Fisher stereo. It could be an iPod or a streaming player like a Roku or Android box. Even a Raspberry PI.
Generally any stereo has RCA inputs but not always 3.5mm Aux input jacks, for that you can buy a adapter "RCA to 3.5mm" to work with just about anything. For a cheap jukebox any old Phone with a SD card or Android box can be made with Kodi to be controllable with a Smartphone and store/play anything you want.