I Am Going To Purchase A EMS Because Of Chronic

I am going to purchase a EMS because of chronic back pain. My internal med doctor just proved my pain is muscular. My phy therapist used a EMS 2 days ago and relief last almost 2 days. I ran out of medicare phy therapy treatments so will be in pain till Jan. I am not willing to wait... for relief. I need to know what EMS you suggest I purchase .. Thank You Patricia L.