I bought my TENS machine and ear clips from http://bodyclock.co.uk/ - but it doesn't look as though they do the one I bought anymore.Which brands tens device and ear clips are you using? Having trouble figuring out what's compatible with what
I think any TENS machine will do provided you can set the pulse rate (Hz) and the pulse width (microseconds); and be able to set a continuous mode. Here's a picture of the controls to look for, although you can get digital ones too.
A TENS machine will come with leads, and the ear clips I bought seem to fit with any standard TENS machine like the one in the picture. I think you can buy pairs of ear clips from Amazon as bodyclock only sell them in packs of 10. Here's an example https://www.amazon.co.uk/d/qid/clip-Electrodes-application-carbon-contacts-machines-connections/B00IAPLN7G/