good TENS Units

Just switching gears, since my situation has changed.

I talked to my PT about trying TENS, and she thinks it can be useful. So she sent me home with a unit to use. Its definitely helping. Now I need to think long term about getting one. I’ve seen several COTHers mention using one. Which units are good?

Right now, I can just feed and blanket my horses. Grooming is difficult. Lunging is impossible. Holding and using whip hurts.

Sorry for short, choppy answers. Typing one handed since very bad things happen when I type with my injured hand.