HANGSUN Handheld Neck Back Massager for Pain Relief Deep Tissue, Double Head Full Body Percussion Massage MG400 for Shoulder, Leg, Foot, Muscles

You don't have to get the most expensive purpose-built name brand one. This has been my go-to for years: https://www.amazon.com/dp/B073ZH14CQ It's nice because the speed is controlled with an analog slider in the handle, so you can adjust it instantly without having to click through 20 useless patterns first.