Objects (Vibrating or Non-) for Back Massages

I like giving my boyfriend massages but I recently found out that I have (mild) carpal tunnel so I'm trying not to move my wrists and hands too much. I've tried using one of those plastic massagers with 4 knobs but he says it's too hard. He doesn't want me to use my hands and hurt myself but my hands obviously feel better.

Does anyone have any suggestions about anything (vibrating or non-vibrating, and on EF or not on it) that would be better for giving back massages? Thanks!