BT6 Pro as TENS unit - hardware for?

Hi, Is there anywhere to get the lead wires/electrodes for the older model Bio-Tuner (BT6 Pro) for use as a TENS unit?
I think SOTA used to sell this as an accessory, but doesn't now.

Seems like I should be able to put it together myself from inexpensive parts if I knew what to get and where, instead of buying it as an overpriced SOTA accessory (much as I love SOTA).

But there could be something special about these parts... no idea.

Has anyone done this? thanks so much. Tweet