Ghost boxes are used mainly as people use positive bias on false positives to get a response.
You could buy an FM / AM radio with digital tuning from an online retailer for $15 or less, all you need to do is jam one of tuning buttons down and you have your own spirit box and pretend to talk to ghosts.
Amazon sell this for $7.22
Does he have a way to listen to the radio at the gym? This might be a neat idea.