Reddit reviews Silicone Bipolar Breast Electrode Pads (135mm pink)

You want to get 2 sets of the TENS pads meant for around nipples, usually shaped like ( ). There's some relatively inexpensive ones that snap into a circle with a bit of cone to it, electrodes on either side, and they go under a bra really well.

You're going to want to set highest frequency, longest pulse width, and scale up the power very very slowly at first. Ideally, something that does a burst mode so it mimics sucking.

I personally use an Ultima 5 along with these type of pads though I have to use adapter leads.

Big thing about tens and upper body, it's a bad idea to attach + on one side of the body cavity and the - on the other, especially around the heart. You want to stick to dual electrodes. Butterfly electrodes work in a pinch.
Try not to place anything over the nipple itself. It's painful, and your nipples WILL get erect, pushing the pad up, making bad contact, and if the power's too high, it can lead to burns. Trust me, bad juju.

Stick with something you can control easily and slowly work up the power on, and she'll get there.
If you need an extra push, research domperidone. When I induce, all I've done in the past was domperidone and TENS. Once things got moving, then regular expression did the trick. I love my TENS unit and use it daily. Any questions, just ask.