MEDVIVE Rechargeable FDA Cleared Tens Unit with 16 Modes and 8 Pads for Natural Pain Relief and Management, Electric Pulse Impulse Mini Massager Muscle Stimulator https://www.amazon.com/dp/B07D5ML4HM/ref=cm_sw_r_cp_api_i_21xbCb6G0ZMFP

There are a lot of videos on YouTube, not brand specific but they’re generally the same.

I purchased one from Amazon. It’s pretty cheap and it works pretty good.https://www.amazon.com/dp/B07D5ML4HM?ref=ppx_pop_mob_ap_share